The brands, and what each is approved for
Tirzepatide is made by Eli Lilly and sold under two brand names. The approvals differ by country.
| Brand | Where | Approved for |
|---|---|---|
| Mounjaro | UK | Type 2 diabetes (age 10 and over) and weight management in adults (Mounjaro SmPC, MHRA, 2026) |
| Mounjaro | US | Type 2 diabetes (age 10 and over), and lowering the risk of heart attack, stroke and heart-related death in adults with type 2 diabetes at high risk (Mounjaro US label, FDA, 2026) |
| Zepbound | US | Weight management in adults, and moderate to severe obstructive sleep apnoea in adults with obesity (Zepbound label, FDA, 2026) |
How the dose steps up
For adult weight management, the UK Mounjaro label (section 4.2) and the US Zepbound label give the same schedule: 2.5 mg once a week for 4 weeks, then 5 mg, with any further increases in 2.5 mg steps after at least 4 weeks on the current dose, up to a maximum of 15 mg a week (Mounjaro SmPC, MHRA, 2026) (Zepbound label, FDA, 2026). The table shows that adult schedule.
The labels differ elsewhere. The US Mounjaro label is for type 2 diabetes: it gives a starting dose of 2.5 mg and says to increase in 2.5 mg steps only if additional glycaemic control is needed (Mounjaro US label, FDA, 2026). For children aged 10 and over with type 2 diabetes, the maximum in both the UK and US Mounjaro labels is 10 mg a week (Mounjaro SmPC, MHRA, 2026) (Mounjaro US label, FDA, 2026). Your prescriber decides your dose.
| Weekly dose | Earliest start | What the label calls it |
|---|---|---|
| 2.5 mg | Week 1 | Starting dose, for 4 weeks |
| 5 mg | Week 5 | Maintenance dose |
| 7.5 mg | After at least 4 weeks on 5 mg | A step between doses |
| 10 mg | After at least 4 weeks on 7.5 mg | Maintenance dose |
| 12.5 mg | After at least 4 weeks on 10 mg | A step between doses |
| 15 mg | After at least 4 weeks on 12.5 mg | Maintenance dose. The maximum |
The adult schedule from section 4.2 of the UK label (Mounjaro SmPC, MHRA, 2026). Each step is 2.5 mg, at least 4 weeks apart. Many people stay on a dose for longer or never go up to 15 mg. Your prescriber decides your dose.
What the trials found
In SURMOUNT-1, 2,539 adults without diabetes took tirzepatide or a placebo for 72 weeks. Average weight change was −15.0% on 5 mg, −19.5% on 10 mg, −20.9% on 15 mg and −3.1% on placebo (SURMOUNT-1, NEJM, 2022).
SURMOUNT-5 compared tirzepatide with semaglutide directly. At 72 weeks, average weight change was −20.2% on tirzepatide and −13.7% on semaglutide, at the highest dose each person could take (SURMOUNT-5 results, ClinicalTrials.gov, 2025).
- Tirzepatide 5 mg
- Tirzepatide 10 mg
- Tirzepatide 15 mg
- Placebo
Digitised from Figure 3 (SURMOUNT-1) of the Zepbound US label, one marker at a time. At week 4 the three dose markers sit almost on top of each other. At week 8 the 10 mg marker is hidden behind the others, so that point is left out. (Zepbound label, FDA, 2026). Points are read off the published chart, so they can be out by about a quarter of a percentage point. They are average results in the trial, not a prediction. Your results will differ.
Show the numbers
| Week | Tirzepatide 5 mg | Tirzepatide 10 mg | Tirzepatide 15 mg | Placebo |
|---|---|---|---|---|
| 4 | −3.3% | −3.3% | −3.2% | −1.1% |
| 8 | −6.0% | Not readable from the published figure | −5.9% | −1.8% |
| 12 | −7.9% | −8.9% | −8.4% | −2.1% |
| 16 | −9.2% | −11.1% | −10.6% | −2.4% |
| 20 | −10.5% | −12.8% | −12.6% | −2.6% |
| 24 | −11.6% | −14.2% | −14.6% | −2.9% |
| 36 | −13.7% | −17.3% | −18.2% | −3.3% |
| 48 | −15.0% | −19.1% | −20.2% | −3.2% |
| 60 | −16.0% | −20.6% | −21.6% | −3.4% |
| 72 | −16.1% | −20.9% | −22.0% | −3.3% |
Stopping matters too. In SURMOUNT-4, people who switched to placebo after 36 weeks regained much of the weight, while those who stayed on tirzepatide kept losing a little more (SURMOUNT-4, JAMA, 2024). See what happens when you stop.
Common side effects
The UK label lists feeling sick, diarrhoea, being sick, constipation, stomach pain, less appetite and tiredness as very common, which means more than 1 in 10 people (Mounjaro SmPC, MHRA, 2026). The US Zepbound label lists those reported by at least 5% of people, including indigestion, injection site reactions, allergic reactions, burping, hair loss and acid reflux (Zepbound label, FDA, 2026).
Stomach side effects in SURMOUNT-1 were mostly mild to moderate and happened mainly while the dose was going up (SURMOUNT-1, NEJM, 2022). Acute pancreatitis is rare but serious; the MHRA strengthened its warnings in January 2026 (MHRA Drug Safety Update, 2026).
Retatrutide is not tirzepatide
Retatrutide is a different Lilly medicine that is still being tested in trials (TRIUMPH-1, NEJM, 2026). It is not approved in the UK, and the MHRA says products sold as retatrutide outside clinical trials are being supplied illegally (MHRA, 2026). As far as we could find, it is not approved anywhere else either.
What to track beyond weight
Weight is one number, and it moves for lots of reasons. The trials also measured waist size. In STEP 1, the average waist shrank by 13.5 cm on semaglutide 2.4 mg and 4.1 cm on placebo (STEP 1, NEJM, 2021). In SURMOUNT-1 it shrank by 14.0 to 18.5 cm on tirzepatide, depending on dose (SURMOUNT-1, NEJM, 2022).
A short record makes appointments easier. You can tell your prescriber what happened, not what you remember.
- Weight, at the same time of day, read as a weekly trend rather than a daily verdict.
- Waist, measured the same way each time: midway between your lowest rib and the top of your hip bone, after breathing out naturally (NICE NG246, 2025).
- Photos from the same four angles, in the same light and clothes.
- Each injection: the date, the dose, where you injected and any reaction.
- Side effects, appetite and how you feel, on the day they happen.
- Protein and strength training, because part of the weight lost is lean mass (why it matters).
Before your next injection.
- Write down your dose and injection day
- Log side effects when they happen
- Weigh in on the same day each week
- Measure your waist the same way
- Take photos in the same light
- Take questions to your prescriber
Where these facts come from.
- Mounjaro KwikPen (tirzepatide) Summary of Product Characteristics. Revised 29 Aug 2026. emc.
- Wegovy FlexTouch (semaglutide) Summary of Product Characteristics. Revised 09/2026. emc.
- SURMOUNT-5 (NCT05822830): tirzepatide vs semaglutide in adults with obesity. Results posted on ClinicalTrials.gov.
- MOUNJARO (tirzepatide) US prescribing information, Eli Lilly. Revised 8/2026. DailyMed.
- ZEPBOUND (tirzepatide) US prescribing information, Eli Lilly. Revised 8/2026. DailyMed.
- Jastreboff AM et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med 2022;387:205-216.
- Aronne LJ et al. Continued treatment with tirzepatide for maintenance of weight reduction in adults with obesity: the SURMOUNT-4 randomized clinical trial. JAMA 2024;331:38-48.
- GLP-1 receptor agonists and dual GLP-1/GIP receptor agonists: strengthened warnings on acute pancreatitis. 29 Jan 2026.
- Jastreboff AM et al. Retatrutide, a triple hormone receptor agonist, for treatment of obesity. N Engl J Med, published online 29 Sep 2026.
- Counterfeit weight loss pens worth £2 million seized by MHRA and West Midlands Police. 15 Oct 2026.
- Wilding JPH et al. Once-weekly semaglutide in adults with overweight or obesity. N Engl J Med 2021;384:989-1002.
- Overweight and obesity management. NICE guideline NG246: identifying and assessing overweight, obesity and central adiposity. Published 14 Jan 2025.
Checked 25 Oct 2026. Trial figures are average results in the trial, not predictions. Labels change; your prescriber and the leaflet in your pack have the current version.
Pip Body Scan is a personal progress record. It is not a medical device and does not give medical advice, diagnose conditions or recommend doses. Speak to your prescriber or another qualified healthcare professional about symptoms, side effects or changes to your treatment.