Glossary
Medical glossary A–Z
Plain-English definitions of the symptoms, conditions, tests, treatments and health-system terms people ask about most — each linked, where we cover it, to a fuller guide.
Medical language can put a barrier between people and their own health. This glossary explains 393 of the terms that come up most often — the words that appear in a clinic letter, a discharge summary or a results printout and stop you reading: everyday symptoms and signs, disease and diagnosis, the body and physiology, tests and what their abbreviations mean, treatments and medicines, evidence and statistics, the care pathways and consent language used around decisions, and the digital-health standards we work with. Definitions are deliberately concise; where we have a fuller page on the topic, follow the link to read more.
These definitions follow you around the site. On our clinical pages, difficult terms are marked with a dotted underline — like this. Select one and a short definition appears, with a link to the full guide where we have one, so you never have to leave the page you are reading to look a word up.
A
- Absolute risk
- Your actual chance of an outcome, expressed as a plain number — for example 2 in 100 over ten years. Evidence, research & statistics
- Active ingredient
- The component of a medicine that produces the effect, as distinct from the fillers, coatings and flavourings around it. Treatment & medicines
- Acute
- Coming on quickly and usually lasting a short time. The opposite of chronic — it describes the speed of onset, not how serious something is. General & disease terms
- Acute-on-chronic
- A sudden worsening (acute flare) on top of a long-standing (chronic) condition — for example an acute chest infection in someone with chronic lung disease. General & disease terms
- Adherence · compliance
- How closely someone takes a medicine as prescribed. Also called compliance or concordance. Treatment & medicines
- Advance decision · living will, ADRT
- A legally binding statement made while a person has capacity, refusing specified treatment in future circumstances. Care pathways, consent & the health system
- Adverse drug reaction · ADR
- A harmful or unpleasant reaction to a medicine at normal use. In the UK these can be reported through the Yellow Card scheme. Treatment & medicines
- Aetiology
- The cause or origin of a disease. General & disease terms
- Afebrile
- Without a fever — body temperature in the normal range. Signs & symptoms
- Albumin
- The main protein in blood. A low level can reflect poor nutrition, liver disease, kidney loss or ongoing illness. Results, values & abbreviations
- ALP
- Alkaline phosphatase — an enzyme raised in bile-duct blockage and in some bone conditions. Results, values & abbreviations
- ALT
- Alanine aminotransferase — a liver enzyme that rises when liver cells are inflamed or damaged. Results, values & abbreviations
- Ambient scribe
- An AI tool that listens to a clinical encounter and drafts documentation; needs safety and DPIA evaluation before adoption. Digital health, assurance & interoperability
- Anaemia
- Too little haemoglobin in the blood to carry oxygen efficiently, causing tiredness, breathlessness and pallor. It is a finding with many causes, not a diagnosis on its own. Read more → General & disease terms
- Analgesia · painkiller
- Pain relief, and the medicines used to provide it. Read more → Treatment & medicines
- Analgesic · painkiller
- A painkiller — a medicine that relieves pain, such as paracetamol or ibuprofen. Treatment & medicines
- Anaphylaxis
- A severe, rapid allergic reaction affecting breathing or circulation. It is a medical emergency needing adrenaline and an ambulance. Read more → Treatment & medicines
- Angio-oedema
- Deeper swelling of the lips, tongue, eyelids or throat. Swelling that affects breathing or swallowing is an emergency. Read more → Signs & symptoms
- Anhedonia
- Losing the ability to take pleasure in things you normally enjoy — a core feature of depression. Read more → Signs & symptoms
- Anorexia
- Loss of appetite. (Distinct from anorexia nervosa, which is an eating disorder.) Signs & symptoms
- Anterior · ventral
- At or towards the front of the body. Body & physiology
- Anti-inflammatory
- A medicine that reduces inflammation, swelling and pain — such as the NSAIDs ibuprofen and naproxen. Read more → Treatment & medicines
- Antibiotic
- A medicine that kills bacteria or stops them growing, used to treat bacterial infections. Antibiotics do not work against viruses. Read more → Treatment & medicines
- Antibody
- A protein made by the immune system that recognises and helps neutralise a specific germ or foreign substance. Body & physiology
- Anticoagulant · blood thinner
- A medicine that reduces the blood’s ability to clot ("blood thinner"), used to prevent or treat harmful clots. Treatment & medicines
- Antimicrobial resistance · AMR
- When bacteria and other microbes evolve so that medicines that used to kill them no longer work. Read more → Treatment & medicines
- Antimicrobial stewardship
- The organised effort to use antibiotics only when needed, and as narrowly and briefly as possible, to slow resistance. Read more → Treatment & medicines
- Antipyretic
- A medicine that brings a fever down. Read more → Treatment & medicines
- Anuria
- Passing virtually no urine at all. Signs & symptoms
- Appraisal
- An annual structured discussion of a doctor’s practice, development and supporting evidence, feeding into revalidation. Medical education & exams
- Arrhythmia
- An abnormal heart rhythm — too fast, too slow or irregular. Read more → Body & physiology
- Arthralgia
- Joint pain, without necessarily any swelling or inflammation. Read more → Signs & symptoms
- Ascites
- A build-up of fluid in the abdomen (tummy), often related to liver disease, causing swelling and discomfort. Read more → Signs & symptoms
- Asymptomatic
- Having a condition but no symptoms from it — common in early high blood pressure and in some infections. Signs & symptoms
- Ataxia
- Loss of coordination and balance causing an unsteady, clumsy gait. Read more → Signs & symptoms
- Atrophy
- Wasting or shrinking of a tissue or organ, such as muscle wasting from disuse. Body & physiology
- Aura
- A warning experience just before a migraine or seizure — often visual zigzags, flashing lights, numbness or an odd smell. Read more → Signs & symptoms
B
- Baseline
- A person’s starting measurement, recorded so later results can be compared against it. Tests & investigations
- Benign
- Not cancerous, and not able to spread to other parts of the body. A benign growth may still need treatment if it causes symptoms, but it is not malignant. General & disease terms
- Benign tumour
- A non-cancerous growth that does not spread to other parts of the body, though it may still need removal if it presses on nearby structures. Body & physiology
- Benign vs malignant
- Benign means not cancerous and unable to spread; malignant means cancerous and able to spread. The distinction guides how urgently and how aggressively something is treated. General & disease terms
- Best interests
- The legal standard for deciding on behalf of someone who lacks capacity, taking account of their past wishes, beliefs and values, not just clinical convenience. Care pathways, consent & the health system
- Bias
- Any systematic flaw in design, conduct or analysis that pushes a result away from the truth in a predictable direction. Evidence, research & statistics
- Bilateral
- Affecting both sides. Body & physiology
- Bilirubin
- A yellow substance from the breakdown of red blood cells; a raised level causes jaundice and can indicate a liver or blood problem. Read more → Tests & investigations
- Bioavailability
- The proportion of a dose that reaches the bloodstream in active form. It explains why an injected and a swallowed version of the same medicine are not interchangeable. Treatment & medicines
- Biologic
- A medicine made from living cells — usually a large protein such as an antibody — given by injection or drip rather than as a tablet. Read more → Treatment & medicines
- Biopsy
- Taking a small sample of tissue so it can be examined under a microscope, usually to check for disease such as cancer. Read more → Tests & investigations
- Biosimilar
- A close but not identical copy of a biologic medicine, approved after demonstrating equivalent safety and effect. Treatment & medicines
- Blinding · masking
- Keeping participants, clinicians or assessors unaware of who received which treatment, so expectation cannot colour the results. Evidence, research & statistics
- Blood gas · ABG, VBG
- A blood test, usually from an artery, measuring oxygen, carbon dioxide and acid-base balance — used in seriously unwell patients. Results, values & abbreviations
- Blood test
- A test on a sample of blood, analysed in a laboratory in many different ways depending on what the doctor is looking for. Read more → Tests & investigations
- BNF
- British National Formulary — the standard UK prescribing reference for doses, interactions and cautions. Treatment & medicines
- Bradycardia
- A slower-than-normal resting heart rate, generally below 60 beats per minute in adults. It can be normal in fit people or a sign of a problem. Signs & symptoms
- Brand name · proprietary name
- A manufacturer’s trade name for a medicine. The same active ingredient may be sold under several brands, which is how people accidentally double up. Treatment & medicines
- Broad spectrum
- An antibiotic active against a wide range of bacteria. Convenient when the organism is unknown, but it disturbs more normal bacteria and drives resistance. Read more → Treatment & medicines
C
- Cachexia
- Severe loss of weight, muscle and strength caused by an underlying illness such as cancer, heart failure or advanced infection. Read more → Signs & symptoms
- Capacity · mental capacity
- The ability to understand, retain and weigh information about a decision and communicate a choice. It is decision-specific and can change over time; it is presumed present unless shown otherwise. Care pathways, consent & the health system
- Cardiovascular
- Relating to the heart and blood vessels. Body & physiology
- Care plan
- A written, agreed summary of someone’s needs, goals, treatments and what to do if things change. Care pathways, consent & the health system
- Case-control study
- A study comparing people who already have a condition with similar people who do not, looking back for differences in exposure. Evidence, research & statistics
- Caution
- Can be used, but with extra care, closer monitoring or an adjusted approach. Treatment & medicines
- Ceiling of treatment
- An agreed limit on how far escalation should go — for example ward-level care but not intensive care — set in advance so decisions are not made in a crisis. Care pathways, consent & the health system
- Chronic
- Long-lasting or persistent, usually meaning three months or more. A chronic condition is ongoing and managed over time rather than cured quickly. General & disease terms
- Claudication · intermittent claudication
- Cramping pain in the legs brought on by walking and relieved by rest, caused by narrowed leg arteries limiting blood supply to the muscles. Read more → Signs & symptoms
- Clinical audit
- A cycle that measures practice against a defined standard, implements change, then re-measures to check for improvement. Medical education & exams
- Clinical governance
- The systems through which an organisation is accountable for the quality and safety of the care it provides. Read more → Care pathways, consent & the health system
- Clinical safety case
- A structured, evidenced argument that a health IT system is acceptably safe for its intended use, owned by a Clinical Safety Officer. Digital health, assurance & interoperability
- Clinical Safety Officer (CSO)
- A suitably qualified clinician accountable for clinical risk management of a health IT system under DCB0129/0160, who owns the clinical safety case and hazard log. Digital health, assurance & interoperability
- Cohort study
- A study following groups over time to see who develops an outcome — good for harms and for long follow-up, but cannot prove cause on its own. Evidence, research & statistics
- Colic
- Pain that comes in waves, building to a peak then easing, typical of a blocked tube such as the ureter or bile duct. Signs & symptoms
- Comorbidity
- Another long-term condition present at the same time as the main one — for example, having both diabetes and high blood pressure. General & disease terms
- Confidence interval · CI
- The range within which the true effect most plausibly lies. A wide interval means real uncertainty; one that crosses "no difference" means the study cannot rule out no effect. Evidence, research & statistics
- Confounding
- When a third factor is linked to both the exposure and the outcome and so distorts the apparent relationship between them. Evidence, research & statistics
- Congenital
- Present from birth. A congenital condition may be inherited or may have developed during pregnancy. General & disease terms
- Conservative management
- Managing a condition without surgery or aggressive intervention — for example with physiotherapy, pain relief and time. Care pathways, consent & the health system
- Contraindicated
- Must not be used in this situation, because the risk of harm is unacceptable. Treatment & medicines
- Contraindication
- A reason not to use a particular treatment because it could be harmful for that person — for example a drug that is unsafe in pregnancy. Treatment & medicines
- Contralateral
- On the opposite side of the body. Body & physiology
- Contrast
- A dye given by mouth or injection to make blood vessels or organs show up more clearly on a scan. Read more → Tests & investigations
- CPD
- Continuing professional development — the ongoing learning clinicians must do and record to stay current. Medical education & exams
- Creatinine
- A waste product from muscle that the kidneys clear. Its blood level is used to estimate how well the kidneys are working. Read more → Results, values & abbreviations
- CRP · C-reactive protein
- C-reactive protein — a blood marker that rises quickly with inflammation or infection and falls quickly as it settles. It shows that inflammation is present, not what is causing it. Results, values & abbreviations
- CT scan
- Computed tomography — a scan that combines many X-ray images into detailed cross-sectional "slice" pictures of the body. Read more → Tests & investigations
- Culture and sensitivity · C&S, MC&S
- Growing bacteria from a sample to identify the organism, then testing which antibiotics kill it. It is what allows treatment to be narrowed from a best guess to a targeted choice. Read more → Tests & investigations
- Cyanosis
- A bluish colour of the skin or lips caused by low oxygen in the blood. Read more → Signs & symptoms
- Cytology
- Examination of individual cells rather than whole tissue — used in cervical screening, for example. Tests & investigations
D
- D-dimer
- A blood test that rises when a clot is breaking down. It is useful mainly for ruling clots out in lower-risk people, because many other things raise it. Read more → Results, values & abbreviations
- DCB0129
- The clinical risk management standard for the manufacturer of a health IT system; produces a clinical safety case and hazard log. Digital health, assurance & interoperability
- DCB0160
- The clinical risk management standard for the healthcare organisation deploying a health IT system; manages local clinical risk. Digital health, assurance & interoperability
- Decompensation
- The point at which the body can no longer compensate for a chronic problem and symptoms break through — for example fluid overload in heart failure. Read more → Signs & symptoms
- Delirium · acute confusion
- A sudden change in mental state — confusion, poor attention, altered alertness — usually triggered by physical illness, infection, pain or medicines. It fluctuates, and it is not the same as dementia. Read more → Signs & symptoms
- Delusion
- A fixed belief held firmly despite clear evidence against it, and not explained by a person’s culture or faith. Signs & symptoms
- Dependence
- A state in which the body has adapted to a substance, so stopping it causes withdrawal. It is not the same as addiction. Read more → Treatment & medicines
- Deprescribing
- Deliberately stopping or reducing medicines that are no longer needed or whose harms now outweigh their benefits — a planned, monitored process, not simply stopping. Treatment & medicines
- Diagnosis
- Identifying the condition causing someone’s symptoms, from the history, examination and any test results. General & disease terms
- Diaphoresis
- Heavy sweating, especially the cold clammy sweat that can accompany a heart attack, low blood sugar or severe pain. Read more → Signs & symptoms
- Differential (diagnosis)
- The ranked list of conditions that could explain a patient’s presentation, worked through with tests and examination — a core clinical-reasoning skill. Medical education & exams
- Differential diagnosis
- The list of possible conditions that could explain a person’s symptoms, which the doctor narrows down with examination and tests. General & disease terms
- Diplopia
- Double vision — seeing two images of a single object. Read more → Signs & symptoms
- Discharge summary
- The letter sent to a GP when someone leaves hospital, setting out what happened, what changed and what needs following up. Care pathways, consent & the health system
- Distal
- Further from the centre of the body. The fingers are distal to the wrist. Body & physiology
- dm+d
- Dictionary of Medicines and Devices — the UK standard terminology for medicines and medical devices, used for safe, consistent prescribing and data exchange. Digital health, assurance & interoperability
- DNACPR · do not attempt CPR
- A recorded decision that cardiopulmonary resuscitation should not be attempted if the heart stops. It applies to CPR alone and does not withdraw any other treatment or care. Care pathways, consent & the health system
- Dose
- The amount of a medicine taken at one time; the dosage is how much and how often it is taken. Treatment & medicines
- DPIA
- Data Protection Impact Assessment — required under UK GDPR for high-risk processing, including most health AI. Digital health, assurance & interoperability
- Drug interaction
- When one medicine changes how another behaves, making it stronger, weaker or more toxic. Food, alcohol and herbal remedies can interact too. Read more → Treatment & medicines
- DSP Toolkit
- Data Security and Protection Toolkit — the annual UK health-system data-security self-assessment for organisations handling health data or systems. Digital health, assurance & interoperability
- DTAC
- Digital Technology Assessment Criteria — the UK health-system baseline assessment across clinical safety, data protection, technical security, interoperability and usability/accessibility. Digital health, assurance & interoperability
- Duty of candour
- The legal and professional duty to tell a patient openly when something has gone wrong with their care, apologise and explain what will be done. Care pathways, consent & the health system
- Dysarthria
- Slurred or poorly formed speech caused by weakness or poor control of the muscles used to speak — the words are chosen correctly but come out wrong. Read more → Signs & symptoms
- Dysphagia
- Difficulty swallowing, which should always be assessed as it can have several causes. Read more → Signs & symptoms
- Dysphasia · aphasia
- Difficulty producing or understanding language itself, because of damage to the language areas of the brain. A key stroke symptom. Read more → Signs & symptoms
- Dyspnoea · breathlessness
- The medical term for breathlessness or shortness of breath. Read more → Signs & symptoms
- Dysuria
- Pain, stinging or burning when passing urine, commonly from a urine infection. Read more → Signs & symptoms
E
- Early satiety
- Feeling full after only a few mouthfuls. Read more → Signs & symptoms
- Ecchymosis
- The medical word for a bruise — blood that has leaked under the skin. Read more → Signs & symptoms
- ECG · EKG
- Electrocardiogram — a recording of the heart’s electrical activity, used to check its rhythm and look for strain or damage. Read more → Tests & investigations
- Echocardiogram · echo
- An ultrasound scan of the heart showing the chambers, valves and how well the heart pumps. Tests & investigations
- eGFR · estimated glomerular filtration rate
- Estimated glomerular filtration rate — a calculated measure of how much blood the kidneys filter each minute, used to stage chronic kidney disease. Read more → Results, values & abbreviations
- Elective
- Planned in advance rather than an emergency. Care pathways, consent & the health system
- Electrolyte
- A salt dissolved in body fluid — sodium, potassium, calcium, magnesium — essential for nerve, muscle and heart function. Read more → Body & physiology
- Embolus
- Something travelling in the bloodstream — usually a clot fragment — that lodges further downstream and blocks a vessel. Read more → Body & physiology
- Empirical treatment
- Treatment started on the best available judgement before test results are back — for example an antibiotic chosen by likely organism, then changed once cultures return. Read more → Treatment & medicines
- Endoscopy
- Looking inside the body using a thin, flexible tube with a camera — for example to examine the stomach or bowel. Read more → Tests & investigations
- Enteric coated · EC
- Coated so a tablet passes through the stomach intact and dissolves in the intestine, to protect either the stomach or the medicine. Treatment & medicines
- Epidemiology
- The study of how often diseases occur in populations, in whom, and why. Evidence, research & statistics
- Erythema
- Redness of the skin caused by increased blood flow, for example in inflammation or infection. Read more → Signs & symptoms
- Escalation
- Stepping care up when someone deteriorates — more monitoring, senior review or transfer to a higher level of care. Read more → Care pathways, consent & the health system
- ESR
- Erythrocyte sedimentation rate — an older, slower-moving marker of inflammation, still useful in conditions such as polymyalgia rheumatica. Read more → Results, values & abbreviations
- Exacerbation · flare-up
- A flare-up — a period when a long-term condition such as asthma or COPD gets acutely worse. Read more → Signs & symptoms
- Excoriation
- A scratch mark or graze in the skin, often from scratching an itch. Signs & symptoms
F
- False negative
- A test that wrongly shows a condition is absent when it is actually present. Tests & investigations
- False positive
- A test that wrongly shows a condition is present when it is not. Tests & investigations
- Ferritin
- The body’s iron store protein. A low ferritin indicates iron deficiency; inflammation can raise it and mask a deficiency. Read more → Results, values & abbreviations
- FHIR
- Fast Healthcare Interoperability Resources — a modern, web-API standard for exchanging health data. Digital health, assurance & interoperability
- Fibrosis
- Scarring — normal tissue replaced by tougher, less functional fibrous tissue. Body & physiology
- Finger clubbing
- Painless broadening and curving of the fingertips and nails, which can be a sign of long-standing lung, heart or bowel disease. Read more → Signs & symptoms
- First-pass metabolism
- Breakdown of a swallowed medicine by the gut wall and liver before it reaches the rest of the body, which is why some medicines have to be given by another route. Treatment & medicines
- Formulary
- An approved list of medicines that clinicians in a particular area or hospital are recommended to prescribe. Treatment & medicines
- Formulation
- The physical form a medicine comes in — tablet, capsule, liquid, patch, inhaler, injection. Changing formulation can change how much is absorbed. Treatment & medicines
- Frailty
- A state of reduced reserve in which a minor illness or change can cause a disproportionate loss of function. It is not the same as age. Read more → Care pathways, consent & the health system
- Full blood count · FBC
- A common blood test that measures red cells, white cells and platelets — used to check for anaemia, infection and many other problems. Read more → Tests & investigations
G
- Gastrointestinal · GI
- Relating to the stomach and intestines — the digestive tract. Body & physiology
- Generic medicine
- A medicine sold under its active-ingredient name rather than a brand name, usually cheaper but equivalent in effect. Treatment & medicines
- Generic name
- The name of the active ingredient itself (paracetamol), as opposed to a manufacturer’s brand name for it. Read more → Treatment & medicines
- Gillick competence
- The test of whether a child under 16 understands enough to consent to their own treatment. Care pathways, consent & the health system
- GMC
- General Medical Council — the body that registers and regulates doctors in the UK and sets the standards they must meet. Medical education & exams
- Guideline
- A structured, evidence-based recommendation on how to manage a condition. Guidelines inform judgement; they do not replace it for an individual patient. Evidence, research & statistics
H
- Haematemesis
- Vomiting blood. This is an emergency — it usually means bleeding somewhere in the upper gut. Signs & symptoms
- Haematochezia
- Passing fresh red blood from the back passage, usually from bleeding lower in the bowel. Read more → Signs & symptoms
- Haematuria · blood in urine
- Blood in the urine, which may be visible or found only on testing. It always needs assessment. Read more → Signs & symptoms
- Haemoglobin · Hb
- The oxygen-carrying protein in red blood cells. A low level is the definition of anaemia. Read more → Results, values & abbreviations
- Haemoptysis
- Coughing up blood or blood-stained mucus from the airways or lungs. Read more → Signs & symptoms
- Haemostasis
- The body’s process for stopping bleeding, involving platelets and clotting proteins. Body & physiology
- Half-life
- The time taken for the amount of a medicine in the body to fall by half. It governs how often a medicine is taken and how long effects persist after stopping. Treatment & medicines
- Hallucination
- Seeing, hearing, feeling or smelling something that is not there. Read more → Signs & symptoms
- Hazard log
- A living record of identified clinical hazards, their risk ratings and the controls that mitigate them, maintained as part of clinical risk management. Digital health, assurance & interoperability
- Hazard ratio · HR
- A comparison of how quickly an outcome happens in two groups over time. Evidence, research & statistics
- HbA1c · glycated haemoglobin
- A blood test reflecting average glucose control over roughly the previous two to three months, used to diagnose and monitor diabetes. Read more → Results, values & abbreviations
- Hepatic
- Relating to the liver. Body & physiology
- Hepatomegaly
- An enlarged liver, found when a doctor examines the abdomen or on a scan. Signs & symptoms
- Hepatotoxic
- Potentially damaging to the liver. Treatment & medicines
- Hereditary · genetic, inherited
- Passed from parents to children through genes. Also called genetic or inherited. General & disease terms
- Histology
- Examination of tissue structure under a microscope, the basis of most cancer diagnoses. Tests & investigations
- HL7 v2
- A long-established health-messaging standard widely used across hospital and laboratory systems. Digital health, assurance & interoperability
- Homeostasis
- The body’s constant balancing of its internal conditions — temperature, fluid, salts, glucose — within a narrow safe range. Body & physiology
- Hormone
- A chemical messenger released into the blood by a gland that controls processes such as growth, metabolism and reproduction. Body & physiology
- Hyperglycaemia · high blood sugar
- A higher-than-normal level of glucose (sugar) in the blood, common in diabetes. Read more → Body & physiology
- Hyperkalaemia
- A raised blood potassium level. Severe hyperkalaemia can affect the heart rhythm and is a medical emergency. Read more → Results, values & abbreviations
- Hypernatraemia
- A high blood sodium level, usually reflecting a lack of water rather than too much salt. Results, values & abbreviations
- Hypersensitivity
- An immune over-reaction to a substance, ranging from a rash to anaphylaxis. Treatment & medicines
- Hypertension · high blood pressure
- Persistently raised blood pressure, which increases the long-term risk of stroke, heart attack and kidney disease. Read more → Body & physiology
- Hypertrophy
- Enlargement of a tissue or organ because its cells grow bigger — for example heart-muscle thickening. Body & physiology
- Hypoglycaemia · low blood sugar
- A lower-than-normal level of blood glucose, which can cause shakiness, sweating and confusion and needs prompt treatment. Read more → Body & physiology
- Hypokalaemia
- A low blood potassium level, which can cause muscle weakness, cramps and heart-rhythm problems. Results, values & abbreviations
- Hyponatraemia
- A low blood sodium level, which can cause confusion, nausea and, if severe or rapid, seizures. Results, values & abbreviations
- Hypotension · low blood pressure
- Blood pressure that is lower than normal, which can cause dizziness or fainting if it drops too far. Body & physiology
- Hypoxaemia
- A low level of oxygen in the blood, measured by a blood gas or estimated with a finger probe. Body & physiology
- Hypoxia
- Too little oxygen reaching the body’s tissues. Body & physiology
I
- Iatrogenic
- Caused by medical care itself — for example a side-effect of treatment or a complication of a procedure. General & disease terms
- Idiopathic
- Arising on its own with no identifiable cause. "Idiopathic" simply means the reason is unknown. General & disease terms
- Idiosyncratic
- An unusual, unpredictable reaction peculiar to one individual rather than a dose-related effect seen in most people. Treatment & medicines
- IMG · international medical graduate
- International medical graduate — a doctor whose primary medical qualification was obtained outside the UK. Read more → Medical education & exams
- Immune system
- The network of cells and organs that defends the body against infection and disease. Body & physiology
- Immunisation · vaccination
- Protecting a person against a disease, usually by vaccination, so the immune system can fight it off in future. Treatment & medicines
- Immunosuppression
- A weakened immune system, whether from illness or from medicines given deliberately to damp it down. It raises the risk and severity of infection. Read more → Treatment & medicines
- Incidence
- How many new cases of a condition appear in a population over a set period, such as a year. General & disease terms
- Incident report
- A formal record of a safety event or near miss, used to learn and change systems rather than to assign blame. Care pathways, consent & the health system
- Incidental finding
- Something unexpected picked up on a scan or test done for another reason. Some need following up and some do not. Tests & investigations
- Infarction
- Death of tissue because its blood supply has been cut off — as in a heart attack (myocardial infarction). Body & physiology
- Inferior
- Below, or lower down, in the body. Body & physiology
- Inflammation
- The body’s natural response to injury or infection — redness, heat, swelling and pain as the immune system reacts and repairs. Body & physiology
- Informed consent
- Agreement to a treatment given voluntarily, with capacity, after being told the realistic benefits, risks and alternatives — including no treatment. Care pathways, consent & the health system
- Inpatient
- Admitted to a hospital bed for at least one night. Care pathways, consent & the health system
- INR
- International normalised ratio — a standardised measure of how long blood takes to clot, used to monitor warfarin. Read more → Results, values & abbreviations
- Insidious onset
- Starting so gradually that the person cannot say when it began. Signs & symptoms
- Intended use
- The precise statement of what a product does, for whom and in what setting. Clear intended use scopes regulatory, clinical-safety and procurement assessment. Digital health, assurance & interoperability
- Intention to treat · ITT
- Analysing everyone in the group they were originally assigned to, even if they stopped or switched. It keeps a trial honest about real-world use. Evidence, research & statistics
- Intramuscular · IM
- Injected into a muscle. Results, values & abbreviations
- Intravenous · IV
- Given directly into a vein, usually through a drip or injection. Treatment & medicines
- Ipsilateral
- On the same side of the body. Body & physiology
- Ischaemia
- A reduced blood supply to a part of the body, which starves the tissue of oxygen and can cause pain or damage. Read more → Body & physiology
J
- Jaundice
- Yellowing of the skin and the whites of the eyes, caused by a build-up of bilirubin, often signalling a liver, bile-duct or blood problem. Read more → Signs & symptoms
L
- Lasting power of attorney · LPA
- A legal arrangement appointing someone to make decisions for you — including about health and care — if you lose capacity. Care pathways, consent & the health system
- Lateral
- Further from the midline — towards the side. Body & physiology
- Lesion
- Any area of abnormal tissue or damage — a broad term covering wounds, ulcers, growths and more. Body & physiology
- Lethargy · fatigue
- A state of tiredness, low energy and reduced alertness. Read more → Signs & symptoms
- Liver function tests · LFTs
- A blood panel of liver enzymes and proteins used to detect liver inflammation, blockage of bile flow or reduced liver function. Results, values & abbreviations
- Loading dose
- A larger initial amount used to reach an effective level quickly, followed by smaller maintenance amounts. Treatment & medicines
- Lumen
- The hollow inside of a tube such as a blood vessel, the bowel or an airway. Body & physiology
- Lymphadenopathy · swollen glands
- Enlarged lymph nodes — the "swollen glands" felt in the neck, armpit or groin, usually reacting to infection. Read more → Signs & symptoms
M
- Macule
- A flat area of altered skin colour that cannot be felt. Signs & symptoms
- Malaise
- A general feeling of being unwell, "off colour" or lacking energy, often an early and non-specific sign of illness. Read more → Signs & symptoms
- Malignant
- Cancerous — able to invade nearby tissue and spread (metastasise) to other parts of the body. General & disease terms
- Medial
- Nearer to the midline of the body. Body & physiology
- Melaena
- Black, tarry, strong-smelling stool caused by bleeding higher up in the digestive tract. It needs urgent assessment. Read more → Signs & symptoms
- Meta-analysis
- Statistically pooling results from several studies to produce one combined estimate, usually inside a systematic review. Evidence, research & statistics
- Metabolism
- All the chemical processes that keep the body working — turning food into energy and building or repairing tissue. Body & physiology
- Metastasis · secondary, mets
- The spread of cancer from where it started to a new part of the body, forming a secondary tumour. General & disease terms
- MHRA
- Medicines and Healthcare products Regulatory Agency — the UK regulator overseeing medicines and medical devices, including software classified as a medical device. Digital health, assurance & interoperability
- Modified release · MR, SR, XL, prolonged release
- A tablet or capsule engineered to release its medicine slowly. It must usually be swallowed whole — crushing or chewing it can release the whole amount at once. Treatment & medicines
- Monoclonal antibody
- A laboratory-made antibody designed to attach to one specific target in the body. Generic names typically end in "-mab". Treatment & medicines
- MRI scan
- Magnetic resonance imaging — a scan that uses a strong magnetic field and radio waves to create detailed images, especially of soft tissues. Read more → Tests & investigations
- Mucosa · mucous membrane
- The moist lining of passages that open to the outside, such as the mouth, gut, airways and bladder. Body & physiology
- Multidisciplinary team · MDT
- A group of professionals from different specialties who review a case together and agree a plan — standard practice in cancer and complex care. Care pathways, consent & the health system
- Myalgia
- Muscle pain or aching. Signs & symptoms
N
- Nausea
- The feeling of being about to be sick (vomit). Signs & symptoms
- Nebuliser
- A machine that turns liquid medicine into a mist to be breathed in, used when an inhaler is not enough. Treatment & medicines
- Necrosis
- Death of tissue, usually because its blood supply or oxygen has been cut off. Dead tissue cannot recover and may need removing. Body & physiology
- Negative predictive value · NPV
- Of the people who test negative, the proportion who really are free of the condition. Evidence, research & statistics
- Nephrotoxic
- Potentially damaging to the kidneys — a reason some medicines are paused during acute illness or dehydration. Read more → Treatment & medicines
- Neurological
- Relating to the brain, spinal cord and nerves. Body & physiology
- Neuropathy · peripheral neuropathy
- Damage to nerves outside the brain and spinal cord, causing numbness, tingling, burning pain or weakness — commonly in the feet. Read more → Signs & symptoms
- Neutropenia
- A low neutrophil count, which raises the risk of serious infection. A fever during neutropenia is a medical emergency. Read more → Results, values & abbreviations
- Neutrophils
- The most common white blood cells and the first responders to bacterial infection. Results, values & abbreviations
- Never event
- A serious, largely preventable patient-safety incident that should never happen if the right barriers are in place. Care pathways, consent & the health system
- NICE
- The National Institute for Health and Care Excellence — the body that produces evidence-based guidance and technology appraisals for England. Care pathways, consent & the health system
- Nil by mouth · NBM
- Nothing to eat or drink, usually before surgery, a procedure or when swallowing is unsafe. Results, values & abbreviations
- Nocturia
- Waking in the night to pass urine. Read more → Signs & symptoms
- Non-inferiority trial
- A trial asking whether a new treatment is not meaningfully worse than the standard one — often because it is cheaper, safer or easier to take. Evidence, research & statistics
- Nosocomial · hospital-acquired
- Acquired in hospital, usually said of an infection. General & disease terms
- NSAID
- Non-steroidal anti-inflammatory drug — a group including ibuprofen and naproxen that eases pain and inflammation but can irritate the stomach and affect the kidneys. Read more → Treatment & medicines
- Number needed to harm · NNH
- How many people need the treatment for one extra person to suffer a given harm. Evidence, research & statistics
- Number needed to treat · NNT
- How many people need the treatment for one of them to benefit. A useful way to judge whether a benefit is worth the burden and side-effects. Evidence, research & statistics
O
- Observational study
- A study that watches what happens in practice without assigning treatment. Useful and realistic, but vulnerable to confounding. Read more → Evidence, research & statistics
- Occlusion
- Complete blockage of a vessel or tube. Body & physiology
- Odds ratio · OR
- A measure of association between an exposure and an outcome, common in case-control studies. Evidence, research & statistics
- Odynophagia
- Pain on swallowing, as distinct from food actually sticking. Signs & symptoms
- Oedema · edema, fluid retention
- Swelling caused by fluid building up in the body’s tissues, often seen in the ankles, legs or feet. Read more → Signs & symptoms
- Oedema (pulmonary)
- Fluid collecting in the lungs, causing breathlessness — often a sign that the heart is not pumping effectively. Body & physiology
- Off-label
- Using a licensed medicine for a purpose, age group or route not covered by its licence. Legal and often appropriate, but it should be explained and documented. Treatment & medicines
- Oliguria
- Passing much less urine than normal — an important warning sign in dehydration and kidney injury. Read more → Signs & symptoms
- Oncology
- The branch of medicine concerned with diagnosing and treating cancer. Body & physiology
- Oral · PO
- Taken by mouth — for example a tablet, capsule or liquid that is swallowed. Treatment & medicines
- Organomegaly
- Enlargement of an internal organ. Signs & symptoms
- Orthopnoea
- Breathlessness that comes on when lying flat and eases on sitting up. Often a sign of fluid on the lungs in heart failure — people describe needing extra pillows to sleep. Read more → Signs & symptoms
- OSCE
- Objective Structured Clinical Examination — a circuit of timed stations assessing clinical and communication skills. Medical education & exams
- Ototoxic
- Potentially damaging to hearing or balance. Read more → Treatment & medicines
- Outpatient
- Seen at a hospital clinic without being admitted to a bed. Care pathways, consent & the health system
P
- p-value
- The probability of seeing a result at least this extreme if there were truly no effect. A small p-value argues against pure chance; it says nothing about how large or important the effect is. Evidence, research & statistics
- Palliative care
- Care that focuses on relieving symptoms and improving quality of life in serious illness, alongside or instead of treatments aimed at cure. Read more → General & disease terms
- Pallor
- Abnormal paleness of the skin, which may point to anaemia or poor circulation. Read more → Signs & symptoms
- Palpitations
- An awareness of your own heartbeat — feeling it racing, pounding, fluttering or skipping. Read more → Signs & symptoms
- Papule
- A small solid raised spot in the skin, less than about half a centimetre across. Signs & symptoms
- Paraesthesia · pins and needles
- Abnormal skin sensations such as tingling, prickling or "pins and needles", often from nerve irritation. Read more → Signs & symptoms
- Paroxysmal nocturnal dyspnoea · PND
- Waking suddenly in the night gasping for breath, then improving after sitting or standing for a while. A recognised warning sign in heart failure. Signs & symptoms
- Pathophysiology
- The mechanism by which a disease produces its effects — what is actually going wrong in the body. General & disease terms
- PDSA cycle
- Plan-Do-Study-Act — the core quality-improvement loop: plan a small change and predict its effect, do it on a small scale, study the result, then act. Medical education & exams
- Perfusion
- The delivery of blood — and so oxygen — to a tissue. Body & physiology
- Peripheral
- At the outer parts of the body or away from the centre — for example the hands and feet, or nerves outside the brain and spinal cord. Body & physiology
- Peripheral oedema
- Fluid swelling in the limbs, usually the ankles and feet, which may leave a dent when pressed (pitting). Read more → Signs & symptoms
- Petechiae
- Tiny flat red or purple pinpoint spots caused by bleeding into the skin, which do not fade when pressed. Signs & symptoms
- Photophobia
- Discomfort or pain in the eyes on exposure to light, which can accompany migraine, eye problems or meningitis. Read more → Signs & symptoms
- PLAB
- Professional and Linguistic Assessments Board — the established route for international medical graduates to GMC registration. Medical education & exams
- Placebo
- A dummy treatment with no active ingredient, used in trials to compare against a real medicine. Treatment & medicines
- Placebo effect
- A real improvement that follows the act of being treated and the expectation of benefit, rather than any active ingredient. Evidence, research & statistics
- Platelets
- Small blood cells that clump together to help stop bleeding. Read more → Results, values & abbreviations
- Point-of-care test · POCT
- A test done and read where the patient is — at the bedside, in a clinic or at home — rather than sent to a laboratory. Tests & investigations
- Polydipsia
- Being abnormally thirsty and drinking much more than usual — one of the classic early signs of diabetes. Read more → Signs & symptoms
- Polypharmacy
- Being on many medicines at once. Sometimes entirely appropriate, but it raises the risk of interactions, side-effects and confusion, and is a reason for regular review. Read more → Treatment & medicines
- Polyuria
- Passing abnormally large volumes of urine. Read more → Signs & symptoms
- Portfolio
- The collected evidence of a clinician’s training, reflection and achievement, used in appraisal, applications and interviews. Medical education & exams
- Positive predictive value · PPV
- Of the people who test positive, the proportion who really do have the condition. It falls sharply when a condition is rare, however good the test is. Evidence, research & statistics
- Positive result
- A test result showing that what was being looked for is present. Whether that is good or bad news depends entirely on the test. Tests & investigations
- Posterior · dorsal
- At or towards the back of the body. Body & physiology
- Postictal
- The recovery period straight after a seizure, when someone may be confused, drowsy, headachy or aching. Read more → Signs & symptoms
- Postural hypotension · orthostatic hypotension
- A drop in blood pressure on standing up, causing light-headedness or a faint. Common in older people and with some medicines. Read more → Body & physiology
- Presyncope
- Feeling about to faint — light-headed, sweaty, greying-out vision — without actually losing consciousness. Read more → Signs & symptoms
- Prevalence
- How common a condition is in a population at a given time — the proportion of people who have it. General & disease terms
- Primary care
- The first point of contact with the health service — general practice, community pharmacy, dentistry and optometry. Care pathways, consent & the health system
- Primary endpoint
- The single main outcome a trial was designed to measure, chosen before it starts. Evidence, research & statistics
- PRN · as required
- From the Latin "pro re nata" — take as needed, rather than at fixed times. Results, values & abbreviations
- Prodrome
- The early warning phase before a condition fully declares itself — such as the aura before a migraine or the vague achiness before flu. Read more → Signs & symptoms
- Prognosis
- The likely course and outcome of a condition — a doctor’s best estimate of what to expect, based on the diagnosis and other factors. General & disease terms
- Prone
- Lying face down. Prone positioning is used deliberately in some patients with severe lung disease to improve oxygen levels. Body & physiology
- Prophylaxis · preventive treatment
- Treatment given to prevent a problem before it happens, rather than to treat an existing one — for example antibiotics before certain surgery. Treatment & medicines
- Proximal
- Nearer to the centre of the body or to the point where a limb attaches. The elbow is proximal to the wrist. Body & physiology
- Pruritus · itch
- The medical term for itching. Read more → Signs & symptoms
- Ptosis
- A drooping upper eyelid. Read more → Signs & symptoms
- Purpura
- Purple-red patches from bleeding under the skin that do not blanch when pressed. A non-blanching rash with fever needs emergency assessment. Read more → Signs & symptoms
- Pustule
- A small raised skin lesion filled with pus. Signs & symptoms
- Pyrexia · fever
- The medical term for a raised body temperature, or fever. Read more → Signs & symptoms
Q
- QT prolongation
- A lengthening of one phase of the heart’s electrical cycle on an ECG, which can rarely trigger a dangerous rhythm. Some medicines add to it, especially in combination. Read more → Treatment & medicines
- Quality Improvement (QI)
- Iterative testing of small changes (for example PDSA cycles) to improve a process over time. Medical education & exams
R
- Radio-opaque
- Blocking X-rays, so it appears white on an X-ray image — bone and metal, for example. Tests & investigations
- Radiolucent
- Allowing X-rays through, so it appears dark on an X-ray image. Tests & investigations
- Randomised controlled trial · RCT
- A study in which participants are allocated by chance to treatment or comparison groups, so the groups are alike apart from the treatment. The strongest single design for asking whether a treatment works. Evidence, research & statistics
- Real-world evidence · RWE
- Evidence drawn from routine care data — records, registries, claims — rather than from a controlled trial. Read more → Evidence, research & statistics
- Red flag
- A specific symptom or sign that raises the possibility of a serious cause and triggers urgent assessment or referral. Signs & symptoms
- Reference range · normal range
- The range of values considered normal for a blood or other test. A result just outside the range is not always a problem and is read alongside symptoms. Tests & investigations
- Referral
- A formal request from one clinician to another asking for specialist assessment or care. Care pathways, consent & the health system
- Refractory
- Not responding to the usual treatment. Treatment & medicines
- Rehabilitation
- Structured support to regain function and independence after illness, injury or surgery. Read more → Care pathways, consent & the health system
- Relapse · flare, recurrence
- The return of a disease or its symptoms after a period of improvement or remission. General & disease terms
- Relative risk · risk ratio, RR
- How much a risk changes in proportion to a baseline — "a 50% increase". Without the absolute risk it can sound far more dramatic than it is. Evidence, research & statistics
- Remission
- A period when the signs and symptoms of a disease are reduced or gone. Remission is not always the same as cure — the condition can return. General & disease terms
- Renal
- Relating to the kidneys. Body & physiology
- Respiratory
- Relating to breathing and the lungs and airways. Body & physiology
- Revalidation
- The five-yearly process by which UK doctors demonstrate they remain fit to practise, built on annual appraisal and supporting evidence. Read more → Medical education & exams
- Risk factor
- Something that increases the chance of developing a condition — such as smoking for heart disease. Having a risk factor does not guarantee the disease. General & disease terms
- RWD
- Real-World Data — the raw data from routine care (records, registries, claims) that, once analysed, becomes real-world evidence. Digital health, assurance & interoperability
- RWE
- Real-World Evidence — clinical evidence generated from routine-care data (electronic records, registries) rather than only trials. Digital health, assurance & interoperability
S
- Safeguarding
- The duty to protect children and adults at risk from abuse or neglect, including a duty to raise concerns. Care pathways, consent & the health system
- SaMD
- Software as a Medical Device — software with a medical purpose that may be regulated as a medical device by the MHRA. Digital health, assurance & interoperability
- Saturation · oxygen saturation, sats, SpO₂
- The percentage of haemoglobin in the blood carrying oxygen, usually measured with a clip on the finger. Tests & investigations
- Screening
- Testing people who have no symptoms to find a condition early, when treatment is more likely to work — for example cervical or bowel screening. Read more → Tests & investigations
- Secondary care
- Hospital-based specialist care, usually reached by referral from primary care. Care pathways, consent & the health system
- Self-management
- The day-to-day work a person does to look after their own long-term condition, supported by education and an agreed plan. Care pathways, consent & the health system
- Sensitivity
- How good a test is at correctly identifying people who do have the condition. A highly sensitive test is good for ruling a condition out when negative. Evidence, research & statistics
- Sepsis
- A life-threatening reaction in which the body’s response to infection begins to damage its own organs. It needs urgent treatment — every hour matters. Read more → General & disease terms
- Sequelae
- Lasting consequences left behind after an illness or injury. General & disease terms
- Serotonin syndrome
- A reaction to too much serotonin activity — agitation, sweating, tremor, fast heart rate, muscle twitching — usually when serotonin-acting medicines are combined. Read more → Treatment & medicines
- Side effect · adverse effect
- An unwanted effect of a medicine that happens alongside its intended action. Treatment & medicines
- Side-effect · adverse effect
- An unwanted effect of a medicine taken correctly. Common ones are usually mild; the important question is which ones mean stop and seek help. Treatment & medicines
- Sinus rhythm
- The heart’s normal rhythm, set by its own natural pacemaker. Body & physiology
- SmPC · Summary of Product Characteristics
- Summary of Product Characteristics — the regulator-approved document giving the full authorised detail on a medicine, including doses. It is the authority our own reference pages point to. Treatment & medicines
- SNOMED CT
- A comprehensive clinical terminology used across UK health systems to code diagnoses, findings and procedures so clinical meaning is shared consistently between systems. Digital health, assurance & interoperability
- Spacer
- A plastic chamber fitted to an inhaler that makes the medicine far easier to breathe deep into the lungs. It improves delivery for most people, not just children. Read more → Treatment & medicines
- Specificity
- How good a test is at correctly identifying people who do not have the condition. A highly specific test is good for ruling a condition in when positive. Evidence, research & statistics
- Spirometry
- A breathing test measuring how much air you can blow out and how fast, used to diagnose and monitor asthma and COPD. Read more → Tests & investigations
- Splenomegaly
- An enlarged spleen, found on examination or a scan. It can point to infection, blood disorders or liver disease, and a very enlarged spleen is vulnerable to injury. Signs & symptoms
- Statistically significant
- Unlikely to be explained by chance alone. It is not the same as clinically important — a tiny effect can be statistically significant in a large study. Evidence, research & statistics
- Steady state
- The point, usually after several half-lives, at which the amount going in balances the amount cleared and levels stop climbing. Treatment & medicines
- Steatorrhoea
- Pale, greasy, floating, hard-to-flush stool that happens when fat is not being absorbed properly. Signs & symptoms
- Stenosis
- Narrowing of a tube, valve or canal. Body & physiology
- Steroid · corticosteroid
- A medicine (corticosteroid) that reduces inflammation and calms the immune system, used in conditions such as asthma, eczema and arthritis. Treatment & medicines
- Subcutaneous · SC, subcut
- Injected into the fatty layer just under the skin. Results, values & abbreviations
- Sublingual · SL
- Placed under the tongue to be absorbed straight into the bloodstream. Read more → Results, values & abbreviations
- Superior
- Above, or higher up, in the body. Body & physiology
- Supine
- Lying flat on the back, face up. Body & physiology
- Surrogate endpoint
- A stand-in measurement — a blood result or scan finding — used instead of an outcome that matters to patients. Improving a surrogate does not guarantee people live longer or feel better. Evidence, research & statistics
- Syncope · fainting
- The medical word for fainting — a brief loss of consciousness caused by a temporary drop in blood flow to the brain. Read more → Signs & symptoms
- Syndrome
- A recognised group of symptoms and signs that tend to occur together, even when the single underlying cause is not fully known. General & disease terms
- Systematic review
- A review that searches for, appraises and summarises all the studies answering a defined question, using a pre-set method to limit bias. Evidence, research & statistics
- Systemic
- Affecting the whole body rather than one area. A systemic medicine works throughout the body; a topical one acts where it is applied. Body & physiology
T
- Tachycardia
- A faster-than-normal resting heart rate, generally above 100 beats per minute in adults. Read more → Signs & symptoms
- Tachypnoea
- Breathing faster than normal for a person’s age. Signs & symptoms
- Tapering · weaning off
- Reducing a medicine in steps rather than stopping it suddenly. Essential for steroids, many antidepressants, benzodiazepines and some heart and epilepsy medicines, where abrupt withdrawal can be dangerous. Read more → Treatment & medicines
- Tenesmus
- A persistent feeling of needing to empty the bowels even when they are already empty. Signs & symptoms
- Teratogenic
- Capable of harming a developing baby in the womb. Some medicines require reliable contraception, and none should be started or stopped in pregnancy without advice. Treatment & medicines
- Terminal
- A condition that cannot be cured and is expected to lead to death, where care focuses on comfort and quality of life. General & disease terms
- Tertiary care
- Highly specialised care in a regional or national centre, for rare or complex problems. Care pathways, consent & the health system
- Therapeutic drug monitoring · TDM
- Measuring the level of a medicine in the blood to keep it inside a safe, effective window. Treatment & medicines
- Therapeutic index
- The gap between an effective amount and a toxic one. A narrow therapeutic index — as with lithium, digoxin or warfarin — means small changes matter and monitoring is required. Read more → Treatment & medicines
- Thrombosis
- The formation of a blood clot inside a vessel, which can restrict or block flow. Read more → Body & physiology
- Thrombus
- A blood clot formed in place inside a blood vessel. Read more → Body & physiology
- Thyroid function tests · TFTs
- Blood tests measuring TSH and thyroid hormones to tell whether the thyroid is underactive or overactive. Read more → Results, values & abbreviations
- Tinnitus
- Hearing a sound — ringing, buzzing or hissing — that has no external source. Read more → Signs & symptoms
- Titration
- Gradually adjusting a medicine’s dose up or down to find the amount that works best with fewest side effects. Treatment & medicines
- Tolerance
- Needing more of a substance over time to get the same effect. Treatment & medicines
- Topical
- Applied directly to the skin or surface of the body, such as a cream or ointment. Read more → Treatment & medicines
- Triage
- Sorting people by clinical urgency so the sickest are seen first — which is why arrival order is not the order of being seen. Care pathways, consent & the health system
- Troponin
- A protein released when heart muscle is damaged. A rising level supports the diagnosis of a heart attack. Results, values & abbreviations
- Trough level
- A blood level measured just before the next dose is due — the point at which the concentration is lowest. Treatment & medicines
- TSH
- Thyroid-stimulating hormone — released by the pituitary to drive the thyroid. Counter-intuitively, a high TSH usually means an underactive thyroid. Read more → Results, values & abbreviations
- Two-week wait · urgent suspected cancer referral
- An urgent English referral pathway requiring someone with symptoms that could indicate cancer to be seen by a specialist within two weeks. Most people referred this way do not turn out to have cancer. Care pathways, consent & the health system
U
- UK GDPR
- The UK data-protection regime that, with the Data Protection Act, governs processing of personal data — including the DPIA requirement for high-risk processing such as most health AI. Digital health, assurance & interoperability
- UKMLA
- UK Medical Licensing Assessment — the GMC common assessment (Applied Knowledge Test plus Clinical and Professional Skills Assessment). Medical education & exams
- Ultrasound
- A scan that uses sound waves to build real-time images of organs and structures, with no radiation. Read more → Tests & investigations
- Unilateral
- Affecting one side only. Body & physiology
- Unlicensed medicine
- A medicine with no UK marketing authorisation for any use, prescribed when no licensed alternative fits — with clear justification. Treatment & medicines
- Urea and electrolytes · U&E, renal profile
- A blood test panel showing kidney function and the main body salts — sodium, potassium, urea and creatinine. Read more → Results, values & abbreviations
- Urinalysis · urine dip
- A bedside dipstick test of urine looking for blood, protein, glucose and signs of infection. Read more → Tests & investigations
- Urticaria · hives, nettle rash
- Raised, itchy weals that come and go, usually within a day, caused by histamine release in the skin. Read more → Signs & symptoms
V
- Vertigo
- A false sense that you or your surroundings are spinning or moving, usually from a problem in the inner ear or balance system. Read more → Signs & symptoms
- Vesicle
- A small fluid-filled skin blister. Read more → Signs & symptoms
W
- Watchful waiting · active monitoring
- Deliberately monitoring a problem rather than treating it immediately, because time itself is informative and treatment may not be needed. Care pathways, consent & the health system
- White cell count · WCC, WBC
- The number of white blood cells, the immune system’s infection-fighting cells. A rise often points to infection or inflammation. Results, values & abbreviations
- Withdrawal
- Symptoms that appear when a medicine or substance the body has adapted to is reduced or stopped. Treatment & medicines
X
- X-ray
- An imaging test using small doses of radiation to show dense structures such as bones. Read more → Tests & investigations
Y
- Yellow Card scheme
- The UK system, run by the MHRA, for anyone — including patients — to report a suspected side-effect of a medicine, vaccine or device. Treatment & medicines
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