A GIP/GLP-1 receptor agonist
Tirzepatide
A once-weekly injection for type 2 diabetes that lowers blood sugar and helps with weight.
What is Tirzepatide?
Tirzepatide is a once-weekly injection used to improve blood sugar control in adults with type 2 diabetes. It is unusual in acting on two gut-hormone pathways at once (GIP and GLP-1), which tends to give strong reductions in blood sugar and body weight. It is given under the skin and is used alongside diet, exercise and often other diabetes medicines.
Education and reference only. This is a plain-language guide to Tirzepatide — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Tirzepatide, sold as Mounjaro, is an injectable medicine for type 2 diabetes. It belongs to the GLP-1 receptor agonist family but is a 'dual agonist': it mimics two natural gut hormones, GIP and GLP-1, rather than one. It is given as an injection under the skin once a week using a pre-filled pen.
How it works
It activates the GIP and GLP-1 receptors, the targets of two hormones the gut releases after eating. This prompts the pancreas to release insulin when blood sugar is high, reduces the release of glucagon (a hormone that raises blood sugar), slows the rate at which the stomach empties, and reduces appetite. Acting on both pathways tends to produce larger falls in blood sugar and weight than single-pathway medicines.
Company & origin
Originated / developed by: Eli Lilly.
United States
What it treats
Conditions Tirzepatide is used for
Practical use
How to take Tirzepatide
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Inject under the skin of the tummy, thigh or upper arm once a week, on the same day each week.
- Rotate the injection site each week to protect the skin.
- It can be given at any time of day, with or without food.
- The dose is increased slowly over time to reduce nausea, so follow the step-up plan you are given.
- If you miss your weekly dose, take it as soon as you can within the allowed window, otherwise skip it; never take two doses close together.
- Store the pen in the fridge and follow the leaflet on keeping it out of the fridge once in use.
Weighing it up
Advantages & disadvantages of Tirzepatide
Advantages
- Once-weekly dosing is convenient and easy to remember.
- Tends to give strong improvements in blood sugar (HbA1c).
- Often leads to meaningful weight loss, which is helpful in type 2 diabetes.
- Low risk of hypos when used on its own.
Disadvantages
- It is an injection, which some people prefer to avoid.
- Nausea, and sometimes vomiting or diarrhoea, are common when starting or stepping up.
- It must be kept refrigerated and used with correct pen technique.
- It is not suitable in type 1 diabetes and is not a substitute for insulin.
Practical use
Good to know
It is injected just once a week, on the same day each week, and because it lowers appetite many people also lose weight. Nausea is the most common early effect and usually settles as the body adjusts, which is why the dose is built up gradually rather than started high. It is not insulin and on its own carries a low risk of hypos, though that risk rises if it is combined with insulin or a sulfonylurea.
Who should not take it / use with caution
- People who have had an allergic reaction to tirzepatide.
- Anyone with a personal or family history of medullary thyroid cancer or the MEN 2 syndrome should not use it.
- People who have had pancreatitis should use it only with specialist advice.
- It is not used in type 1 diabetes or for diabetic ketoacidosis.
- It is not recommended in pregnancy or while breastfeeding.
Monitoring
- Blood sugar control (HbA1c) is checked periodically.
- Weight is monitored.
- Be alert for symptoms of pancreatitis or gallbladder problems.
Side effects
- Nausea, vomiting, diarrhoea or constipation, especially early on.
- Reduced appetite and indigestion.
- Injection-site reactions such as redness or itching.
- Rarely, gallbladder problems or inflammation of the pancreas (severe, persistent tummy pain that may spread to the back needs urgent help).
Key interactions
- Combining it with insulin or a sulfonylurea raises the risk of hypos, so those doses may need lowering.
- By slowing stomach emptying it can change how quickly other tablets are absorbed.
- Tell your team if you take medicines for which timing of absorption matters.
Available as: Available as a pre-filled injection pen for use under the skin.
Answers
Tirzepatide: frequently asked questions
How often do I take tirzepatide?
It is injected under the skin once a week, on the same day each week. It can be given at any time of day, with or without food.
Will it make me lose weight?
Many people do lose weight on tirzepatide because it reduces appetite, and this can be helpful in type 2 diabetes. The amount varies from person to person.
Can it cause a hypo?
On its own the risk of a hypo is low. The risk increases if it is combined with insulin or a sulfonylurea, in which case those doses may be reduced.
Why does the dose go up gradually?
Starting low and increasing slowly helps reduce nausea and other gut effects, which are the most common reason people feel unwell at first.
What if I feel severe tummy pain?
Severe, persistent tummy pain, especially if it spreads to your back and comes with vomiting, can signal inflammation of the pancreas and needs urgent medical attention.
The wider class
About GLP-1 receptor agonists
Tirzepatide belongs to the glp-1 receptor agonists class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF
- NICE CKS
Building a medicines information resource?
We create evidence-led, dose-free drug and formulary references for teams.