Quick answer: in the main trial of tirzepatide weight loss, adults without diabetes lost an average of 15.0% of their body weight on 5 mg, 19.5% on 10 mg and 20.9% on 15 mg over 72 weeks, compared with 3.1% on placebo.[1] For someone who starts at 230 lb, that is roughly 35 to 48 lb. People with type 2 diabetes lost less, about 13% to 15%.[2]
Tirzepatide is sold as Zepbound for weight management and Mounjaro for type 2 diabetes. Below are the results from each SURMOUNT trial, what real-world data show, and why some people lose more than others. For an overview of the drug, see our tirzepatide profile.
SURMOUNT trial results by dose
| Trial | Who took part | Dose | Weeks | Weight change | Placebo |
|---|---|---|---|---|---|
| SURMOUNT-1 | 2,539 adults with obesity, no diabetes | 5 / 10 / 15 mg | 72 | −15.0% / −19.5% / −20.9% | −3.1%[1] |
| SURMOUNT-2 | 938 adults with obesity and type 2 diabetes | 10 / 15 mg | 72 | −12.8% / −14.7% | −3.2%[2] |
| SURMOUNT-3 | 579 adults who first lost ≥5% with intensive lifestyle change | 10 or 15 mg | 72 | A further −18.4% | +2.5%[3] |
| SURMOUNT-4 | 783 adults, 36 weeks open-label, then randomized | 10 or 15 mg | 88 | −25.3% overall if continued | −9.9% if switched to placebo[4] |
| SURMOUNT-5 | 751 adults, tirzepatide vs semaglutide | 10 or 15 mg | 72 | −20.2% | Semaglutide −13.7%[5] |
A few patterns stand out:
- Dose matters. In SURMOUNT-1, the share losing at least 20% of their weight was 50% on 10 mg and 57% on 15 mg, versus 3% on placebo.[1]
- Most people reach a meaningful threshold. At least 5% weight loss was reached by 85%, 89% and 91% of people on 5, 10 and 15 mg.[1]
- Weight loss is smaller with type 2 diabetes. SURMOUNT-2 participants lost about 6 to 7 percentage points less than SURMOUNT-1 participants on the same doses.[1][2]
- Lifestyle change plus tirzepatide adds up. In SURMOUNT-3, 44.7% of people on tirzepatide lost a further 20% or more after a 12-week lifestyle program.[6]
For the doses and how they are reached, see the tirzepatide dosage chart.
Week-by-week: how fast the weight comes off
Weight loss on tirzepatide is gradual because the dose rises slowly. In SURMOUNT-1, the dose started at 2.5 mg and increased every 4 weeks, so the 15 mg group did not reach its full dose until week 20.[1]
| Time point | What the data show |
|---|---|
| Weeks 1-4 | Starting dose (2.5 mg), used to let the body adjust rather than for maximum effect[6] |
| Week 12 | 82% of consistent SURMOUNT-1 users had lost at least 5%[7] |
| Week 24 | 70% of the slower starters had reached 5%[7] |
| Week 72 | Average loss of 15% to 21%, depending on dose[1] |
| Week 176 | Loss of 12.3% to 19.7% maintained in people with prediabetes who stayed on treatment[11] |
The timeline for appetite and blood sugar is covered in how long does tirzepatide take to work.
Responders and slower responders
Not everyone responds at the same speed. A post hoc analysis of 1,545 SURMOUNT-1 participants who took at least 75% of their doses compared people by their weight loss at week 12:[7]
- Early responders (82%) had lost at least 5% by week 12.
- Late responders (18%) had lost less than 5%. They were more likely to be male and started at a higher weight.
- Most late responders caught up: 70% reached 5% weight loss by week 24 and 90% by week 72. It took them about 25 weeks on average.[7]
A separate analysis of SURMOUNT-1 and SURMOUNT-2 used a week-8 cutoff. Early responders went on to lose more weight and saw bigger improvements in blood pressure, blood sugar and lipids. Both groups still achieved clinically meaningful weight loss, and gastrointestinal side effects were similar in both.[8]
If progress seems slow, our guide to not losing weight on a GLP-1 covers common reasons.
What predicts how much you lose
No test predicts an individual result, but the trials point to several factors:
- Dose: in SURMOUNT-1, average loss rose from 15.0% on 5 mg to 20.9% on 15 mg.[1]
- Diabetes: people with type 2 diabetes lost less on the same doses.[2]
- Early response: losing at least 5% by week 8 or 12 was linked to more weight loss by week 72, although slower starters usually still reached meaningful results.[7][8]
- Sex and starting weight: slower starters were more likely to be male and to begin at a higher weight.[7]
- Staying on treatment: in the UK cohort, people who ordered their medicine more regularly lost more weight.[10] In SURMOUNT-4, stopping led to regain.[4]
- Lifestyle: the trials combined tirzepatide with a reduced-calorie diet and more activity.[6]
Real-world weight loss
Real-world results are usually smaller than trial results, because people miss doses, stop early or stay on lower doses.
- US health systems (2024): among 18,386 matched adults, people on tirzepatide lost more weight than people on semaglutide at 3, 6 and 12 months. At 12 months the difference was 6.9 percentage points. More than half of each group stopped treatment during follow-up.[9]
- UK digital prescribing cohort (2026): among over 630,000 self-paying adults, average self-reported weight loss was 13.5% at 6 months and 17.4% at 12 months. At 6 months, 89.9% had lost at least 5%. Many reached these results without going to the top doses.[10]
Weight loss with sleep apnea
In the SURMOUNT-OSA trials of adults with obesity and moderate to severe sleep apnea, people on tirzepatide 10 or 15 mg lost 17.7% to 19.6% of their body weight over 52 weeks, versus 1.6% to 2.3% on placebo.[6] See Zepbound sleep apnea.
Tirzepatide vs semaglutide
In SURMOUNT-5, the only head-to-head obesity trial, tirzepatide produced 20.2% weight loss versus 13.7% with semaglutide over 72 weeks.[5] Our semaglutide profile covers that drug’s own trials.
What happens after you stop
In SURMOUNT-4, people who switched to placebo after 36 weeks regained 14.0% of their body weight over the next year. Those who stayed on tirzepatide lost a further 5.5%.[4] See our guide to the tirzepatide maintenance dose for newer data on lower-dose maintenance.
