What is tirzepatide?
It is an ingredient of a prescription medicine, not a supplement. In the EU, Mounjaro is used for type 2 diabetes and weight management in adults who meet specific criteria. Treatment is combined with changes to nutrition and physical activity. [24]
This page mainly discusses use in adults. Body weight alone or a medicine's popularity should not determine a treatment decision.
How does it work in the body?
Tirzepatide mimics two hormones: GIP and GLP-1. They are part of the body's response to food. The medicine helps regulate insulin secretion and lower blood sugar, and also reduces appetite. [24]
Acting on two types of receptor, the sites that receive signals in cells, does not automatically mean twice the benefit. Effectiveness is established by human studies, not simply by the number of mechanisms.
Who is treatment intended for?
The weight-management indication covers adults with obesity or overweight accompanied by a weight-related health condition. Mounjaro is given using an injection pen. Selecting treatment requires assessing health and existing medicines. [24]
Exact EU indications
Weight management: a BMI of at least 30, or 27 and above with a weight-related condition. BMI compares weight with height. The separate type 2 diabetes indication now covers adults and children aged 10 and over. This does not mean approval for treating obesity in children. [25]
How much weight loss was shown?
In a large study of people without diabetes, average weight loss with tirzepatide ranged from about 15% to 21%, depending on the dose studied. Follow-up lasted 72 weeks. [26]
At a starting weight of 100 kg, a 15–21% reduction is equivalent to 15–21 kg. This converts average results from different groups, not a prediction for an individual.
Detailed SURMOUNT-1 results
2,539 adults with obesity or overweight with a complication, without diabetes. Tirzepatide groups at 5, 10 and 15 mg: −15.0%, −19.5% and −20.9%. Treatment discontinuation due to adverse effects in these groups: 4.3%, 7.1% and 6.2%, respectively. The analysis included discontinuations. Doses describe the trial, not instructions for self-treatment. [26]
Can weight return after stopping treatment?
Yes. In a study where some participants continued treatment and others switched to placebo, weight regain was observed after stopping treatment. People who continued treatment maintained more of the weight change they had achieved. [27]
This matters when planning treatment: reaching a lower weight is one stage, and maintaining it is another. The results should not be read as advice to stop treatment or change the dose independently.
How was stopping treatment studied?
In SURMOUNT-4, after 36 weeks of treatment, 670 participants were randomly assigned to continue tirzepatide or receive placebo for 52 weeks. Among those continuing tirzepatide, weight fell by a further average of 5.5% relative to weight at week 36. This was a selected group who reached the second stage, not everyone starting treatment. [27]
What do we know about the risk of developing diabetes?
During three-year follow-up of people with obesity and prediabetes, diabetes was diagnosed less often during tirzepatide treatment than with placebo. Prediabetes means raised blood sugar that does not yet meet the criteria for diabetes. [29]
The result applies to a particular group. It does not prove that the medicine will prevent diabetes in everyone, and does not itself create a new treatment indication.
Numbers from longer follow-up
1,032 participants with prediabetes; after 176 weeks, diabetes was diagnosed in 1.3% of those treated with tirzepatide. After a further 17 weeks without treatment, the proportion in the same group was 2.4%. [29]
Which side effects can occur?
The most common effects are digestive: nausea, diarrhoea, vomiting, constipation and abdominal pain. Fluid loss can cause dehydration and worsen kidney function. Combined with insulin or certain other medicines, blood glucose may fall too low. [25]
Severe, persistent abdominal pain, particularly when spreading to the back, requires urgent medical contact. Shortness of breath or sudden swelling of the tongue and throat requires immediate help. [25]
Tirzepatide is not used during pregnancy. Plans for pregnancy and breastfeeding should be discussed with a doctor. Before anaesthesia, tell the team about the medicine because it slows stomach emptying. [25]
What is useful to know before discussing treatment?
Mounjaro is approved in the EU and requires a prescription. Availability of a particular pack and reimbursement in Poland are separate matters; European authorization alone does not establish them. [24]
Prepare a list of your medicines, previous health problems and treatments before an appointment. This helps you discuss benefits and risks in your own situation.
What do more recent studies show?
Mounjaro in the abdomen, thigh or upper arm? Why it is injected under the skin
Tirzepatide: what do we know about maintaining weight loss? — a separate article about the 2026 study and other more recent findings.
We read the cited publications as the authors' summaries. The studies discussed were funded by Lilly. We did not assess the full texts.
Where does this information come from?
Show sources and how they were checked
- EMA: Mounjaro — opis leku
EU regulator · description updated 18 August 2026 · page reviewed. Accessed: 2 November 2026.
- EMA: Mounjaro — informacja o produkcie
EU regulator · updated 21.09.2026 · English safety sections and patient leaflet read, not the entire PDF. Accessed: 02.11.2026.
- Jastreboff i wsp.: tirzepatyd w badaniu SURMOUNT-1
Study publication · 04.06.2022 online · PubMed abstract read. Accessed: 02.11.2026.
- Aronne i wsp.: kontynuacja lub odstawienie tirzepatydu, SURMOUNT-4
Study publication · JAMA, 2 January 2024 · PubMed abstract reviewed. Accessed: 2 November 2026.
- Jastreboff et al.: tirzepatide, obesity and the development of diabetes
Study publication · online 13 November 2024, NEJM issue 6 March 2025 · PubMed abstract reviewed. Accessed: 2 November 2026.