Which works better for weight loss: semaglutide or tirzepatide?
Tirzepatide produces greater weight loss and better blood sugar control than semaglutide on average. Gastrointestinal complaints occur equally often with both medications, but the difference in serious adverse events is a point to discuss with your doctor.
Tirzepatide beats semaglutide on almost every measure. The difference lies in how they work: semaglutide targets a single hormone receptor (GLP-1), while tirzepatide simultaneously activates a second receptor (GIP) as well. This dual approach explains its stronger effect.
In people with overweight or obesity who do not have diabetes, a network meta-analysis of 27 studies (n=15,584) shows that tirzepatide 15 mg reduces body weight by an average of 16.53% compared with placebo, more than semaglutide 2.4 mg1. A large study using real-world patient data (n=18,386) confirms this: tirzepatide users were 1.76 times more likely to achieve at least 5% weight loss and 3.24 times more likely to achieve at least 15%, compared with semaglutide users. After 12 months, the average difference was 6.9 percentage points in favour of tirzepatide2.
In type 2 diabetes, a network meta-analysis of 28 studies (n=23,622) confirms the same picture3. In a head-to-head comparison (SURPASS-2, n=1,879, 40 weeks), tirzepatide reduced average blood sugar over the preceding months by 2.01 to 2.30 percentage points, compared with 1.86 percentage points for semaglutide 1 mg. In terms of weight, tirzepatide users lost 1.9 to 5.5 kg more, depending on the dose. All three tirzepatide doses (5, 10 and 15 mg per week) were statistically superior4.
Gastrointestinal complaints such as nausea, diarrhoea and vomiting occur equally often with both medications and are usually mild. In SURPASS-2, the rates were close: nausea 17-22% (tirzepatide) versus 18% (semaglutide), diarrhoea 13-16% versus 12%, vomiting 6-10% versus 8%. At higher doses of tirzepatide, complaints occurred slightly more often.
One point of attention: in SURPASS-2, serious adverse events were reported slightly more often with tirzepatide (5-7%) than with semaglutide (3%). Broader meta-analyses did find that neither medication increases the risk of serious adverse events compared with placebo5,6. What caused the difference in that one study is unclear. Discuss this with your doctor before making a decision.
Sources are two network meta-analyses (PMID 38613667, 39305981), one meta-analysis of randomised trials (PMID 37253796), one direct randomised trial (SURPASS-2, PMID 34170647), one large observational study using electronic patient records (PMID 38976257) and one additional meta-analysis for adverse events (PMID 38286487). The observational study is not a randomised trial and may overestimate the benefits of tirzepatide due to bias.