The first clear results of tirzepatide usually show after about three months. In an analysis of the SURMOUNT-1 trial, 82 percent of participants lost at least 5 percent of their body weight by week 12. After 72 weeks the average loss was 15.0 to 20.9 percent, depending on the dose. If you want to know what to expect after a month, after a quarter and after a year, below you will find the figures from successive trials, week by week.
What happens in the first month?
The first month is mainly about introducing the dose, not about the full effect. In the trials, tirzepatide was started at 2.5 mg once a week. Every four weeks the dose was raised by 2.5 mg until the target dose was reached. In SURMOUNT-1 the whole dose-escalation period lasted 20 weeks.
That is why the result after four weeks says little about the final result. The published analyses do not report the average weight loss after the first month separately. The first measurement point the researchers described in detail is week 12. By then most participants had already had two dose increases.
How many people lose weight clearly after 3 months?
After 12 weeks, 82 percent of participants had lost at least 5 percent of their body weight. This figure comes from a SURMOUNT-1 analysis published in 2025 in Diabetes, Obesity and Metabolism. It covered 1545 people who took at least 75 percent of the planned doses. The researchers called them early responders.
The remaining 18 percent, or 278 people, lost less than 5 percent by week 12. Men were more common among them, 45 versus 30 percent in the fast group. They also weighed more at the start, on average 110.2 versus 103.6 kg. A slower start did not mean no effect, however, as the next section shows.
What if weight falls more slowly after 3 months?
A slower start usually evens out, just later. By week 24, 70 percent of people with a slower start had passed the 5 percent threshold. By week 72 it was 90 percent of that group. On average they needed 24.8 weeks to reach a 5 percent weight loss.
The difference between the groups did remain visible until the end of the trial. People with a fast start lost an average of 22.5 percent after 72 weeks, or 23.2 kg. People with a slower start lost 11.0 percent, or 12.0 kg. The table shows how the result depended on the dose in both groups.
| Tirzepatide dose | Fast start, loss after 72 weeks | Slower start, loss after 72 weeks |
|---|---|---|
| 5 mg | 18.4 percent | 8.3 percent |
| 10 mg | 24.1 percent | 11.4 percent |
| 15 mg | 24.9 percent | 13.6 percent |
The authors conclude that an assessment at 12 weeks is too early to judge treatment a failure. Longer use allows many people to reach a meaningful weight loss.
How much weight can you lose after 9 months?
After 36 weeks, roughly nine months, the average loss was 20.9 percent. This is the result of the SURMOUNT-4 trial, published in 2024 in JAMA. Its first, open-label part enrolled 783 adults with obesity, or overweight with a related condition. Everyone received the highest tolerated dose, 10 or 15 mg.
The 20.9 percent figure refers to the 670 people who completed those 36 weeks. This is an important caveat, because people who stopped treatment earlier are not in that average. Even so, the result shows that most of the effect appears in the first three quarters.
What result do the full 72 weeks give?
After 72 weeks the average weight loss was 15.0 percent at 5 mg, 19.5 percent at 10 mg and 20.9 percent at 15 mg. In the placebo group weight fell by 3.1 percent. This is the main result of SURMOUNT-1, published in 2022 in the New England Journal of Medicine. It included 2539 adults with an average body weight of 104.8 kg.
| Result after 72 weeks | 5 mg | 10 mg | 15 mg | Placebo |
|---|---|---|---|---|
| Average weight loss | 15.0 percent | 19.5 percent | 20.9 percent | 3.1 percent |
| Loss of at least 5 percent | 85 percent of people | 89 percent of people | 91 percent of people | 35 percent of people |
At 10 and 15 mg, 50 and 57 percent of participants respectively lost at least 20 percent of their body weight. In the placebo group 3 percent reached that result.
The figures in the table include all participants, also those who stopped treatment. The most common side effects were gastrointestinal and appeared mainly during dose escalation. Between 4.3 and 7.1 percent of people on tirzepatide stopped treatment because of them.
What happens after a year and beyond?
With continued use, body weight kept falling or stayed at a lower level. In SURMOUNT-4, people who continued tirzepatide from week 36 to week 88 lost an additional 5.5 percent. Their total loss from the start reached 25.3 percent. As many as 89.5 percent of them kept at least 80 percent of their earlier loss.
People switched to placebo regained 14.0 percent of their weight over the same period. The authors state plainly that stopping tirzepatide led to a clear weight regain. That is why in the trials the effect is treated as linked to continued use.
The longest data come from the three-year part of SURMOUNT-1, published in 2025. It covered 1032 people with obesity and prediabetes, treated for 176 weeks. After three years weight loss was 12.3 percent at 5 mg, 18.7 percent at 10 mg and 19.7 percent at 15 mg. Type 2 diabetes was diagnosed in 1.3 percent of people on tirzepatide and in 13.3 percent on placebo.
What does the pace of weight loss on tirzepatide depend on?
The pace depends first of all on the dose, and secondly on the person. A higher dose gave a greater loss both at 24 and at 72 weeks. A 2026 analysis of SURMOUNT-1 and SURMOUNT-2 found that women were more often among the faster responders. That group also had fewer people with high blood sugar at the start.
Practice outside clinical trials gives a similar picture. An analysis of medical records of 10,339 people on tirzepatide and the same number on semaglutide appeared in 2026. Tirzepatide gave an average weight loss of 2.54 percent per month, semaglutide 2.18 percent. A loss of at least 15 percent in the first year was reached by 42.6 percent of people on tirzepatide.
- Dose. 15 mg gave the largest loss at every measurement point.
- Sex. Women were more often in the fast-start group.
- Starting weight. People who were heavier at the start more often began slowly.
- Time. Most of the effect appears in the first 36 weeks, after which the pace slows.
How to track progress over the months?
The simplest way is to measure body weight at the same points as the researchers: at the start and after 12, 24 and 36 weeks. Comparing yourself with trial data only makes sense with a similar measurement rhythm. Next to weight it is worth noting waist circumference, because it changes together with body fat. Which measurements matter is covered in more detail in the guide on how to measure peptide results.
Tirzepatide acts on two receptors at once, GLP-1 and GIP, and this sets it apart from semaglutide. The mechanism is described in the guide on tirzepatide, GLP-1 and GIP. A comparison of three molecules for body weight is in the guide semaglutide vs tirzepatide vs retatrutide.
How much does tirzepatide cost in the shop?
In the shop, tirzepatide comes in three versions from three manufacturers. Tirzepatide 20 mg Bio-Peptide costs 200 EUR and is in stock. Tirzepatide 20 mg Genheal costs 200 EUR and is available on backorder. Tirzepatide 40 mg Nouveaux in a pen costs 350 EUR, so 8.75 EUR per milligram instead of 10 EUR.
How many weeks one vial lasts at successive doses is calculated in the guide on how long a GLP-1 vial lasts. All versions and the price per milligram are on the tirzepatide page. The products in the shop are material for laboratory research, not the medicine Mounjaro.
Frequently asked questions
When do the first effects of tirzepatide show?
In the SURMOUNT-1 analysis, 82 percent of participants lost at least 5 percent of their body weight by week 12. The first month is mainly about introducing the dose from 2.5 mg.
How much weight can you lose on tirzepatide in a year?
After 72 weeks in SURMOUNT-1 the average loss was 15.0 to 20.9 percent of body weight, depending on the dose. After 36 weeks in SURMOUNT-4 it was 20.9 percent at a dose of 10 or 15 mg.
What if the effect is weak after 3 months?
Among people who lost less than 5 percent by week 12, 90 percent passed that threshold by week 72. On average it took them 24.8 weeks.
Does the effect of tirzepatide last after stopping?
In SURMOUNT-4, people switched to placebo regained 14.0 percent of their body weight within 52 weeks. People who continued tirzepatide lost an additional 5.5 percent over the same time.
How long has tirzepatide been studied?
The longest data cover 176 weeks, more than three years. Weight loss then ranged from 12.3 to 19.7 percent, depending on the dose.
Sources
- Jastreboff AM, Aronne LJ, Ahmad NN et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine, 2022, 387(3): 205-216. https://doi.org/10.1056/NEJMoa2206038
- Ard J, Lee CJ, Gudzune K et al. Weight reduction over time in tirzepatide-treated participants by early weight loss response: Post hoc analysis in SURMOUNT-1. Diabetes, Obesity and Metabolism, 2025, 27(9): 5064-5071. https://doi.org/10.1111/dom.16554
- Kokkinos A, Thethi T, Lee CJ et al. Tirzepatide Efficacy and Tolerability According to Early Weight Response: A Post Hoc Analysis of the SURMOUNT-1 and SURMOUNT-2 Trials. Diabetes, Obesity and Metabolism, 2026, 28(9): 8367-8377. https://doi.org/10.1111/dom.71009
- Aronne LJ, Sattar N, Horn DB et al. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA, 2024, 331(1): 38-48. https://doi.org/10.1001/jama.2023.24945
- Jastreboff AM, le Roux CW, Stefanski A et al. Tirzepatide for Obesity Treatment and Diabetes Prevention. New England Journal of Medicine, 2025, 392(10): 958-971. https://doi.org/10.1056/NEJMoa2410819
- Venkatakrishnan AJ, Murugadoss K, Soundararajan V. Weight-loss dynamics with tirzepatide versus semaglutide. PNAS Nexus, 2026, 5(6): pgag171. https://doi.org/10.1093/pnasnexus/pgag171