The average, week by week
These numbers come from SURMOUNT-1, the main weight trial of tirzepatide, the medicine in Mounjaro. 2,539 adults without diabetes took it or a placebo for 72 weeks, with diet and activity counselling for everyone (SURMOUNT-1, NEJM, 2022).
| Week | 15 mg group's dose that week | 5 mg group | 10 mg group | 15 mg group | Placebo |
|---|---|---|---|---|---|
| Week 4 | 2.5 mg | −3.3% | −3.3% | −3.2% | −1.1% |
| Week 8 | 5 mg | −6.0% | Not readable from the published figure | −5.9% | −1.8% |
| Week 12 | 7.5 mg | −7.9% | −8.9% | −8.4% | −2.1% |
| Week 16 | 10 mg | −9.2% | −11.1% | −10.6% | −2.4% |
| Week 20 | 12.5 mg | −10.5% | −12.8% | −12.6% | −2.6% |
| Week 24 | 15 mg | −11.6% | −14.2% | −14.6% | −2.9% |
| Week 36 | 15 mg | −13.7% | −17.3% | −18.2% | −3.3% |
| Week 48 | 15 mg | −15.0% | −19.1% | −20.2% | −3.2% |
| Week 60 | 15 mg | −16.0% | −20.6% | −21.6% | −3.4% |
| Week 72 | 15 mg | −16.1% | −20.9% | −22.0% | −3.3% |
Read off Figure 3 of the US Zepbound label (Zepbound label, FDA, 2026). Each dose's marker was read separately. 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 cell says it is not readable from the published figure. Week 72 values are the ones printed on the chart. In the trial, doses went up by 2.5 mg every 4 weeks until each group reached its dose, so the 5 mg group stayed on 5 mg from week 5 (SURMOUNT-1, NEJM, 2022). Averages in the trial, not a prediction. Your results will differ.
- 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% |
The dose alongside
For adults, the UK label's weight-management schedule is 2.5 mg for 4 weeks, then 5 mg. After that, the dose can go up by 2.5 mg after at least 4 weeks on each dose, to a maximum of 15 mg (Mounjaro SmPC, MHRA, 2026). The table's dose column is the fastest the label allows, which is also how the trial's 15 mg group stepped up (SURMOUNT-1, NEJM, 2022).
Plenty of people stay on a dose for longer, or stay on 5 mg or 10 mg. That is a decision for you and your prescriber. See the Mounjaro guide for the full dose table.
Weeks 1 to 12: side effects come first
Less appetite is very common on Mounjaro (Mounjaro SmPC, MHRA, 2026). In SURMOUNT-1, stomach side effects such as feeling sick and diarrhoea were mostly mild to moderate and happened mainly while the dose was going up (SURMOUNT-1, NEJM, 2022).
Average weight loss in this stage was small and steady: about 3% at week 4, when the three dose markers sit almost on top of each other on the chart, and 8 to 9% at week 12, when they start to separate (Zepbound label, FDA, 2026).
Weeks 16 to 72: the doses spread out, then slow
From week 16 the higher doses pull ahead. By week 72 the averages printed on the label's chart were −16.1% on 5 mg, −20.9% on 10 mg and −22.0% on 15 mg, against −3.3% on placebo (Zepbound label, FDA, 2026).
The paper's headline averages, which count people who stopped treatment differently, were −15.0%, −19.5% and −20.9% (SURMOUNT-1, NEJM, 2022). The paper says the 5 mg group had reached a plateau by week 72 and the higher doses were close to one (SURMOUNT-1, NEJM, 2022). More on plateaus.
What the averages hide
An average sits in the middle of a wide spread. On 15 mg, 90.9% lost at least 5% of their weight, 56.7% lost at least 20% and 36.2% lost at least 25% (SURMOUNT-1, NEJM, 2022). Some people lost much less.
If you have lost less than 5% of your starting weight after 6 months on the highest dose you can tolerate, NICE says a decision is needed about whether to carry on (NICE TA1026, 2024).
Make your own week by week.
- Weigh in on the same day each week
- Note your dose for that week
- Measure your waist every few weeks
- Take photos from the same four angles
- Log side effects as they happen
- Compare months, not days
Where these facts come from.
- 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.
- Mounjaro KwikPen (tirzepatide) Summary of Product Characteristics. Revised 29 Aug 2026. emc.
- Tirzepatide for managing overweight and obesity. NICE technology appraisal guidance TA1026. Published 23 Dec 2024, updated 1 Sep 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.