Chest
Coughing up blood
Coughing up blood or blood-streaked phlegm from the lungs or airways — which always needs prompt medical assessment, and which, when it comes with sudden breathlessness or chest pain, can signal a clot on the lung and is an emergency.
Education and reference only. This explains the common causes of coughing up blood and the warning signs that need urgent help, in plain language — it is not a diagnosis or a substitute for advice from a clinician. If you feel very unwell or are worried, seek medical help.
Quick answer
What is coughing up blood?
Coughing up blood, known medically as haemoptysis, means blood coming from the lungs or airways rather than from the nose, mouth or stomach. Even a small amount of coughed-up blood should always be checked promptly, because while the cause is often a treatable chest infection, it can also be a sign of more serious disease such as tuberculosis, a clot on the lung or, importantly, lung cancer — which is why it must never be ignored.
- Get urgent help: Call 999 if coughing up blood comes with sudden breathlessness, sharp chest pain or feeling faint — this can mean a clot on the lung. Call 999 for coughing up a large amount of blood, or blood that keeps coming.
- Self-care: Coughing up blood is not a symptom to manage with self-care alone — it always needs medical assessment to find the cause, even if you feel otherwise well.
About coughing up blood
Coughing up blood, known medically as haemoptysis, means blood coming from the lungs or airways rather than from the nose, mouth or stomach. Even a small amount of coughed-up blood should always be checked promptly, because while the cause is often a treatable chest infection, it can also be a sign of more serious disease such as tuberculosis, a clot on the lung or, importantly, lung cancer — which is why it must never be ignored. Blood-streaked phlegm during a heavy chest infection that quickly settles as the infection clears is usually less worrying, but persistent or unexplained blood, or larger amounts, needs urgent attention. The most time-critical situation is coughing up blood together with sudden breathlessness, sharp chest pain or a swollen, painful calf, which raises the possibility of a clot that has travelled to the lung and is a medical emergency.
When to get help
Call 999 or go to A&E if coughing up blood comes with any of these warning signs:
- Call 999 if coughing up blood comes with sudden breathlessness, sharp chest pain or feeling faint — this can mean a clot on the lung.
- Call 999 for coughing up a large amount of blood, or blood that keeps coming.
- Seek urgent help for coughing up blood with a swollen, painful or red calf, which can point to a clot.
- Seek urgent help for any coughed-up blood that is unexplained or persistent, even in small amounts.
- Seek urgent help for coughing up blood with a persistent cough, weight loss, night sweats or fever.
When to see a doctor
Coughing up blood always needs prompt medical attention. Call 999 if it comes with sudden breathlessness, sharp chest pain or feeling faint, as this can mean a clot on the lung, or if you are coughing up a large amount of blood. Seek urgent same-day assessment for any coughed-up blood that is unexplained or persistent, even small streaks, and for blood with a long-standing cough, weight loss, night sweats or fever, so that serious causes such as infection, a clot or cancer can be looked for and treated.
Not sure how urgent it is? It is always OK to call NHS 111 for advice, day or night.
What can cause it
Common causes of coughing up blood
Coughing up blood has many possible causes. Each links to a full, plain-language guide to that condition — what it is, how it's treated and when to seek help.
What helps
Self-care and what you can do
Coughing up blood is not a symptom to manage with self-care alone — it always needs medical assessment to find the cause, even if you feel otherwise well. While arranging to be seen, it helps to note how much blood there is, whether it is bright red or just streaks in phlegm, how often it is happening, and any other symptoms such as fever, weight loss, night sweats or breathlessness, as this information guides your clinician. If you smoke, stopping is one of the most important things you can do for your lungs and reduces the risk of serious lung disease. Do not ignore even small amounts of coughed-up blood in the hope it will pass, and seek emergency help straight away if breathlessness or chest pain develops.
Answers
Coughing up blood: frequently asked questions
Is coughing up blood always serious?
Coughing up blood always needs to be checked, even small amounts. While it is often due to a treatable chest infection, it can also signal more serious conditions such as a clot on the lung, tuberculosis or lung cancer, so it should never be ignored.
When is coughing up blood an emergency?
Call 999 if you cough up blood together with sudden breathlessness, sharp chest pain or feeling faint, as this can mean a clot on the lung, or if you are coughing up a large amount of blood or it keeps coming.
How can I tell if blood is coming from my lungs or somewhere else?
Blood from the lungs is usually coughed up and may be frothy or mixed with phlegm, while blood from the nose or stomach reaches the mouth differently. If you are unsure where coughed-up blood is coming from, have it assessed promptly.
I only saw a few streaks of blood in my phlegm — do I still need to see a doctor?
Yes. Even a few streaks of blood in phlegm should be assessed, especially if it is unexplained, keeps happening, or comes with a persistent cough, weight loss or night sweats. Prompt checking allows serious causes to be found early.
Sources
Where this is drawn from
- NICE CKS: Haemoptysis.
- Asthma + Lung UK: coughing up blood.
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