Analysis
Semaglutide vs tirzepatide: which loses more weight?
Across their pivotal trials, tirzepatide produced more average weight loss (~20.9% in SURMOUNT-1) than semaglutide (~14.9% in STEP 1). But these are d
Across their pivotal trials, tirzepatide produced more average weight loss (~20.9% in SURMOUNT-1) than semaglutide (~14.9% in STEP 1). But these are different trials in different populations, so the gap is indicative, not a matched head-to-head. Semaglutide has cardiovascular-outcome evidence and an approved oral form that tirzepatide lacks.
The full picture
The headline numbers are real: semaglutide's STEP 1 landed near 15% mean weight loss, while tirzepatide's SURMOUNT-1 reached about 21% at the top dose. Tirzepatide's dual GIP/GLP-1 mechanism is the leading explanation for the larger effect. If maximum average weight loss is the only goal, tirzepatide has the edge.
But 'more weight loss' isn't the whole decision. Semaglutide carries the SELECT cardiovascular-outcome result and an approved oral option (Rybelsus, for diabetes); tirzepatide adds a sleep-apnea indication. Tolerability, cost, and medical history routinely tip the choice in practice.
The cross-trial caveat matters for anyone quoting these numbers: the two percentages come from separate studies with different enrollment, so treating '21 vs 15' as a precise head-to-head margin overstates what the data can support. The direction is reliable; the exact gap is not.
Headline mean weight loss, approved products (%) — different trials/populations — not a matched head-to-head
| Trial | Design | N | Result | Source | ID |
|---|---|---|---|---|---|
| STEP 1 | RCT, 68 weeks, placebo-controlled | 1,961 | Mean weight change about -14.9% vs -2.4% placebo | N Engl J Med 2021 | NCT03548935 · PMID 33567185 · DOI |
| SURMOUNT-1 | RCT, 72 weeks, placebo-controlled | 2,539 | Up to about -20.9% at 15 mg vs -3.1% placebo | N Engl J Med 2022 | NCT04184622 · PMID 35658024 · DOI |
| SELECT | RCT, CV outcomes | 17,604 | About 20% reduction in major adverse cardiovascular events | N Engl J Med 2023 | NCT03574597 · PMID 37952131 · DOI |
Machine-readable: studies.json.
Frequently asked questions
Is tirzepatide better than semaglutide?
On average weight loss, tirzepatide is higher, but in different trials. Semaglutide has cardiovascular-outcome data and an oral form. 'Better' depends on the person.
Can you compare the percentages directly?
Not precisely — they're from separate trials, so the gap is indicative rather than a matched result.
Related: evidence database · cost calculator · semaglutide · tirzepatide.
Not medical advice. This page is consumer education, not medical advice, and does not recommend a dose, product, or provider. Compounded medications are not FDA approved. Talk with a licensed clinician about your situation.