What this page establishes
- In SURMOUNT-5, 751 adults were randomised to maximum tolerated tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg) for 72 weeks. Mean weight loss was 20.2% versus 13.7% (22.8 kg versus 15.0 kg), p<0.001.
- SURMOUNT-5 also reported waist circumference reduction of 18.4 cm on tirzepatide versus 13.0 cm on semaglutide.
- Zepbound is licensed for long-term weight reduction and for moderate to severe obstructive sleep apnoea in adults with obesity.
- Wegovy is licensed for long-term weight reduction and for cardiovascular risk reduction in adults with established cardiovascular disease and obesity or overweight.
Quick answers
Is Zepbound better than Wegovy?
For average weight loss over 72 weeks in the one trial that compared them directly, tirzepatide produced more: 20.2% against 13.7%.
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"Better" beyond that depends on why you are taking it. Wegovy carries a cardiovascular risk reduction indication that Zepbound does not, and Zepbound carries a sleep apnoea indication that Wegovy does not.Was the trial fair?
It compared maximum tolerated doses rather than equivalent doses, which is a defensible design for a practical question and a limitation for a pharmacological one.
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It cannot separate a better drug from a higher relative dose.Does the difference hold for people with type 2 diabetes?
SURMOUNT-5 excluded diabetes. The tirzepatide-versus-semaglutide comparison in type 2 diabetes is SURPASS-2, which measured HbA1c rather than weight as its primary endpoint.
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This is the comparison that has an actual answer. SURMOUNT-5 randomised people to tirzepatide or semaglutide and measured them against each other, which almost no pair of brands in this class can claim. At 72 weeks the tirzepatide arm lost 20.2% of body weight and the semaglutide arm 13.7%.
What the trial actually did
SURMOUNT-5 (NCT05822830) enrolled 751 adults with obesity, or overweight with a weight-related condition and without diabetes, and randomised them to maximum tolerated doses of tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg) for 72 weeks.
Mean weight loss was 20.2% on tirzepatide against 13.7% on semaglutide, p<0.001, or 22.8 kg against 15.0 kg. Waist circumference fell 18.4 cm against 13.0 cm.
This is a real difference measured in one population under one protocol. It is not two separate trials placed side by side, which is how almost every other brand comparison on the internet is assembled.
What it does not tell you
It does not tell you the difference is the second receptor. Tirzepatide acts at GIP as well as GLP-1, and it is tempting to credit the gap to that, but the trial compared two drugs at their maximum tolerated doses rather than at equivalent ones. There is no way to separate "better drug" from "higher relative dose" inside this design.
It does not tell you what happens to an individual. A 6.5 percentage point difference in means says nothing certain about any one person, and 21% of the semaglutide arm still hit 15% weight loss early.
It does not cover the licences. Zepbound also carries an obstructive sleep apnoea indication, Wegovy carries a cardiovascular risk reduction indication in established cardiovascular disease. Those are different reasons to prescribe and the weight number does not rank them.
Where the two brands differ on paper
Wegovy is semaglutide, 0.25 to 2.4 mg weekly, licensed for weight in adults and children 12 and over and for cardiovascular risk reduction in established cardiovascular disease with obesity or overweight.
Zepbound is tirzepatide, 2.5 to 15 mg weekly, licensed for weight in adults and for moderate to severe obstructive sleep apnoea in adults with obesity.
Both carry a boxed warning for thyroid C-cell tumours.
The evidence, one row per claim
| Claim | Tier | Source |
|---|---|---|
| In SURMOUNT-5, 751 adults were randomised to maximum tolerated tirzepatide (10 or 15 mg) or semaglutide (1.7 or 2.4 mg) for 72 weeks. Mean weight loss was 20.2% versus 13.7% (22.8 kg versus 15.0 kg), p<0.001. | established | SURMOUNT-5 (NCT05822830), American College of Cardiology journal scan |
| SURMOUNT-5 also reported waist circumference reduction of 18.4 cm on tirzepatide versus 13.0 cm on semaglutide. | established | SURMOUNT-5 (NCT05822830), American College of Cardiology journal scan |
| Zepbound is licensed for long-term weight reduction and for moderate to severe obstructive sleep apnoea in adults with obesity. | established | FDA Structured Product Label, NDA217806 (via openFDA) |
| Wegovy is licensed for long-term weight reduction and for cardiovascular risk reduction in adults with established cardiovascular disease and obesity or overweight. | established | FDA Structured Product Label, NDA215256 (via openFDA) |
Questions people ask
How big is 6.5 percentage points in practice?
In this trial, about 7.8 kg between the group means. For an individual it is not predictive: the spread within each arm was far wider than the gap between them.
Sources
- SURMOUNT-5 (NCT05822830), American College of Cardiology journal scan
- FDA Structured Product Label, NDA217806 (via openFDA)
- FDA Structured Product Label, NDA215256 (via openFDA)
Keep reading
- Mounjaro vs Zepbound: One Molecule, Two Licences, Same DosesThe same drug at the same doses. Unlike Ozempic and Wegovy, not even the dose range differs.
- Ozempic vs Mounjaro: The Diabetes Head-to-HeadBoth are licensed for diabetes, and unusually for this category there is a randomised trial of one against the
- Ozempic vs Wegovy: Same Drug, Different Licence and Maximum DoseTwo brands, one molecule. The difference is regulatory and it is only 0.4 mg wide.
- Foundayo vs Wegovy: The Oral Option and the InjectionThe most-asked new comparison in this category, and the one where the honest answer is that nobody has run the