Short answer
Mounjaro is the brand name of tirzepatide, a once-weekly injection that acts on two gut hormone receptors, GIP and GLP-1. In the approval trial, adults with obesity lost on average 15 to 21 per cent of their body weight over 72 weeks. Whether tirzepatide is right for you is a medical decision; at OpenClinic24 a doctor assesses this by video.
Key facts
Tirzepatide acts on two receptors (GIP and GLP-1) and is injected under the skin once a week.
SURMOUNT-1 (NEJM 2022, 2,539 participants): weight change of minus 15.0 / 19.5 / 20.9 per cent after 72 weeks with 5 / 10 / 15 mg, minus 3.1 per cent with placebo.
SURMOUNT-5 (NEJM 2025, 751 participants): tirzepatide minus 20.2 per cent versus semaglutide minus 13.7 per cent after 72 weeks.
For weight management from a BMI of 30, or 27 with a weight-related condition, always alongside diet and exercise.
Tirzepatide can reduce the effect of the contraceptive pill; use additional contraception for four weeks after starting and after each dose increase.
What Mounjaro is and how tirzepatide works
Mounjaro is the brand name of the active substance tirzepatide. Tirzepatide belongs to a new group of medicines that act on two gut hormone receptors: the receptor for GIP (glucose-dependent insulinotropic polypeptide) and the receptor for GLP-1 (glucagon-like peptide 1). Both hormones are released in the gut after a meal. They signal fullness to the brain, slow stomach emptying and increase insulin release when blood sugar is raised.
This dual action distinguishes tirzepatide from semaglutide, the active substance in Ozempic and Wegovy, which works on the GLP-1 receptor only. In everyday life the effect mostly means less hunger and earlier fullness. Many people describe that constant thoughts about food become quieter, which is exactly where conventional diets often fail, because the body responds to weight loss with more appetite.
Tirzepatide is injected once a week under the skin with a prefilled pen, in the abdomen, thigh or upper arm. In the EU it has been approved for type 2 diabetes since 2022 and for weight management since the end of 2023. The binding details on use, contraindications and side effects are set out in the product information within the European Medicines Agency’s assessment report.
What the trials show
Tirzepatide has been studied in a large programme called SURMOUNT. All participants, including those on placebo, also received diet and exercise counselling.
| Trial | Question | Duration | Result with tirzepatide | Comparison |
|---|---|---|---|---|
| SURMOUNT-1 (NEJM 2022) | obesity without diabetes, 2,539 participants | 72 weeks | minus 15.0 / 19.5 / 20.9 % with 5 / 10 / 15 mg | placebo minus 3.1 % |
| SURMOUNT-3 (Nature Medicine 2023) | after 12 weeks of intensive lifestyle programme | 72 weeks | a further minus 18.4 % | placebo gain of 2.5 % |
| SURMOUNT-4 (JAMA 2024) | continuing or switching to placebo after 36 weeks | 88 weeks | weeks 36 to 88: minus 5.5 % | placebo plus 14.0 % |
| SURMOUNT-5 (NEJM 2025) | head-to-head with semaglutide, 751 participants | 72 weeks | minus 20.2 % | semaglutide minus 13.7 % |
In SURMOUNT-1, average starting weight was 104.8 kilograms with a body mass index of 38.0. Weight loss was substantial at every dose and was maintained throughout the trial. SURMOUNT-3 showed that tirzepatide still works strongly in people who have already lost weight on an intensive programme.
Two trials compare tirzepatide directly with semaglutide. In people with type 2 diabetes, tirzepatide lowered long-term blood sugar (HbA1c) by 2.01 to 2.30 percentage points over 40 weeks, semaglutide 1 mg by 1.86 points (Frías and colleagues, NEJM 2021, 1,879 participants). In obesity without diabetes, weight loss after 72 weeks was greater with tirzepatide (SURMOUNT-5). A detailed comparison is in Wegovy or Mounjaro.
In obstructive sleep apnoea with obesity, breathing pauses per hour fell by 25.3 with tirzepatide and by 5.3 with placebo in the first of two trials (Malhotra and colleagues, NEJM 2024), from an average of 51.5 events per hour, which is severe sleep apnoea.
Who may be eligible
For weight management, tirzepatide is approved for adults with a body mass index of at least 30, or at least 27 with a weight-related condition such as high blood pressure, prediabetes or type 2 diabetes, abnormal blood lipids, obstructive sleep apnoea or cardiovascular disease. The German S3 guideline on obesity sees medication as one part of an overall plan of diet, exercise and behaviour change when the basic programme alone is not enough.
It is not used in pregnancy and breastfeeding, with known hypersensitivity, with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2, or with severe digestive disorders such as gastroparesis. Caution applies after previous pancreatitis, with gallstones, diabetic eye disease and when insulin or sulfonylureas are taken at the same time, because low blood sugar can occur. Criteria and process are covered in Getting a weight loss injection prescribed.
Weight loss with medical support
A doctor assesses by video whether a medical treatment is an option for you and then supports you with a plan and follow-up appointments. The decision is made case by case.
Check eligibility in 5 questionsDosing and everyday use
Treatment starts with 2.5 mg once a week. After at least four weeks the dose is raised in steps of 2.5 mg until a maintenance dose of 5, 10 or 15 mg is reached that works and is tolerated. The maximum dose is 15 mg a week. Slow escalation is the best protection against nausea; if a step is poorly tolerated, it is kept for longer.
The injection is given on a fixed day of the week, regardless of meals. A missed dose can be taken within four days; if more time has passed, it is skipped. Small portions, eating slowly, little fat and alcohol at first and enough fluids help. A protein-rich diet and strength training preserve muscle, because without training part of the weight loss comes from muscle.
One point that is often overlooked: tirzepatide can reduce absorption of the contraceptive pill because the stomach empties more slowly. The product information advises additional barrier contraception, or a non-oral method, for four weeks after starting and after each dose increase. Before surgery under anaesthesia, the anaesthetic team should know about the treatment.
Side effects in perspective
The most common side effects affect the digestive tract: nausea, diarrhoea, constipation and vomiting, mainly in the first weeks and after dose increases, usually mild to moderate. Less common but important are gallstones and inflammation of the gallbladder, more frequent with rapid weight loss, and pancreatitis. A full overview with warning signs is in Side effects of weight loss injections.
What happens after stopping
Tirzepatide treats obesity; it does not cure it. In SURMOUNT-4, everyone first took tirzepatide for 36 weeks and lost 20.9 per cent on average. Half then switched to placebo and regained 14.0 per cent over the next 52 weeks, while those who continued lost a further 5.5 per cent. Treatment is therefore planned for the long term; see Stopping weight loss injections.
Costs and insurance in Germany
For weight reduction, statutory health insurance does not cover tirzepatide, because § 34 SGB V (German Social Code, Book V) excludes medicines for weight loss and appetite control. For type 2 diabetes it can be prescribed at the insurer’s expense if the criteria are met. Private insurers decide according to the policy; asking in writing before starting is worthwhile. Medical services are billed under the German fee schedule for doctors (GOÄ). The overview article is Weight loss injections.
When you need urgent medical help
Call 112 for severe upper abdominal pain radiating to the back, shortness of breath or facial swelling after the injection, and confusion. For ongoing vomiting, signs of dehydration or yellowing skin outside surgery hours, call the German on-call medical service on 116 117. Pause the next injection until a doctor has assessed the situation.
When you need help immediately
- Severe, persistent upper abdominal pain, often radiating to the back, with nausea or vomiting: possible pancreatitis
- Ongoing vomiting or diarrhoea with signs of dehydration: very little urine, dizziness, racing heart
- Colicky pain in the upper right abdomen, fever or yellowing of skin and eyes: possible gallstones
- Swelling of the face, lips or tongue, shortness of breath or a rash all over the body after the injection
- Shaking, sweating, confusion while also taking insulin or sulfonylureas: possible low blood sugar
With these warning signs call the emergency number 112. Outside office hours the medical on-call service is available on 116 117. In these situations a video consultation does not replace an in-person examination.
Sources
- Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). New England Journal of Medicine, 2022. DOI: 10.1056/NEJMoa2206038 Study
- Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5). New England Journal of Medicine, 2025. DOI: 10.1056/NEJMoa2416394 Study
- Tirzepatide after intensive lifestyle intervention in adults with overweight or obesity: the SURMOUNT-3 trial. Nature Medicine, 2023. DOI: 10.1038/s41591-023-02597-w Study
- Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity (SURMOUNT-4). JAMA, 2024. DOI: 10.1001/jama.2023.24945 Study
- Tirzepatide for the Treatment of Obstructive Sleep Apnea and Obesity. New England Journal of Medicine, 2024. DOI: 10.1056/NEJMoa2404881 Study
- Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. New England Journal of Medicine, 2021. DOI: 10.1056/NEJMoa2107519 Study
- Mounjaro (tirzepatide): European public assessment report (EPAR) and product information. European Medicines Agency (EMA), 2025. Authority
- S3 guideline Obesity: prevention and treatment (AWMF register number 050-001). German Obesity Society, AWMF, 2024. Guideline
- § 34 German Social Code, Book V: excluded medicines. Federal Ministry of Justice, gesetze-im-internet.de, 2026. Law
All sources were retrieved during the medical review. Studies are linked by DOI; guidelines and laws in their current version.
Frequently Asked Questions
What is Mounjaro and how does it work?
Mounjaro is the brand name of tirzepatide. The medicine mimics two gut hormones, GIP and GLP-1, that are released after a meal. It strengthens the feeling of fullness, reduces appetite, slows stomach emptying and lowers blood sugar when it is raised. Tirzepatide is injected under the skin once a week with a prefilled pen, usually in the abdomen or thigh.
How much weight do people lose with Mounjaro?
In the approval trial SURMOUNT-1, adults with obesity without diabetes lost on average 15.0 per cent with 5 mg, 19.5 per cent with 10 mg and 20.9 per cent with 15 mg after 72 weeks, compared with 3.1 per cent on placebo. All groups also received diet and exercise counselling. Individual results vary widely; averages are not a promise for any one person.
From which BMI can tirzepatide be used for weight loss?
For weight management, tirzepatide is approved for adults with a body mass index of 30 or more, or 27 or more with at least one weight-related condition such as high blood pressure, prediabetes, abnormal blood lipids, sleep apnoea or cardiovascular disease. It complements diet and exercise and does not replace them. Whether it suits you is decided by a doctor.
How is Mounjaro dosed?
Treatment starts with 2.5 mg once a week for four weeks. The dose is then increased in steps of 2.5 mg at intervals of at least four weeks, up to an individual maintenance dose of 5, 10 or 15 mg. If a step is poorly tolerated, it is kept for longer. A missed dose can be taken within four days; otherwise it is skipped.
What are the side effects of tirzepatide?
The most common are digestive symptoms: nausea, diarrhoea, constipation and vomiting, usually mild to moderate and mainly during dose escalation. Less common are gallstones, inflammation of the pancreas and injection site reactions. Severe, persistent abdominal pain or ongoing vomiting should be assessed by a doctor straight away.
Does the pill still work while taking Mounjaro?
Tirzepatide slows stomach emptying and can reduce absorption of the contraceptive pill. The product information advises women using oral contraception to add a barrier method, or switch to a non-oral method, for four weeks after starting and for four weeks after each dose increase. Raise this explicitly in your consultation if contraception or a wish for children is relevant.
Does tirzepatide help with sleep apnoea?
In two trials in people with moderate to severe obstructive sleep apnoea and obesity, the number of breathing pauses per hour fell much more with tirzepatide than with placebo; in the first trial by 25.3 versus 5.3 events per hour. That is a strong argument where sleep apnoea and excess weight coincide, although sleep apnoea itself should still be managed by sleep medicine specialists.
Does German health insurance pay for Mounjaro?
For weight loss, statutory health insurance does not pay, because § 34 SGB V (German Social Code, Book V) explicitly excludes medicines for weight reduction. For type 2 diabetes, tirzepatide can be prescribed as a diabetes medicine at the insurer’s expense if the criteria are met. Private insurers decide according to the policy and medical justification.
About the author
Note: This article provides general information and does not replace individual medical advice, diagnosis or treatment. If you have symptoms, contact a doctor; in an emergency call 112.
