Tirzepatide vs. Semaglutide: Which GLP-1 Leads to More Weight Loss?

In the head-to-head SURMOUNT-5 trial, adults with obesity (without type 2 diabetes) taking the maximum tolerated dose of tirzepatide lost 20.2% of their body weight at 72 weeks, versus 13.7% for those taking maximum tolerated semaglutide — a statistically significant difference (P<0.001). Tirzepatide also produced greater waist circumference reduction and higher rates of reaching 10%, 15%, 20%, and 25% weight-loss thresholds. It was superior on the primary endpoint, but individual response, GI tolerability, and access still matter.

Zepbound is the weight-management brand of tirzepatide, a dual GIP/GLP-1 receptor agonist. Wegovy is the weight-management brand of semaglutide, a GLP-1 receptor agonist. Both are FDA-approved for chronic weight management and injected once weekly. The key difference is mechanism: tirzepatide activates both GIP and GLP-1 receptors, which may drive the larger average weight loss seen in head-to-head trials.

In SURMOUNT-5, average weight loss at 72 weeks was 20.2% of body weight with tirzepatide (10 or 15 mg) and 13.7% with semaglutide (1.7 or 2.4 mg). A network meta-analysis in type 2 diabetes estimated weight reductions from 9.57 kg with tirzepatide 15 mg down to 2.52 kg with semaglutide 0.5 mg — with each tirzepatide dose superior to its semaglutide counterpart. Results vary by person.

Both cause nausea, vomiting, diarrhea, and constipation, mostly during dose escalation. In SURMOUNT-5, the most common adverse events were gastrointestinal in both groups, and most were mild to moderate. A meta-analysis of 26,894 participants without diabetes found GI adverse events were 1.86 times higher than placebo with both agents, but the relative risk was higher with tirzepatide (RR 2.94) than semaglutide (RR 1.68). Neither drug increased serious adverse events or severe hypoglycemia in the type 2 diabetes network meta-analysis.

A network meta-analysis of 28 randomized trials (23,622 participants) found tirzepatide 15 mg reduced HbA1c the most (-1.96%), followed by tirzepatide 10 mg (-1.84%) and semaglutide 2.0 mg (-1.59%). All tirzepatide doses were comparable to semaglutide 2.0 mg and superior to semaglutide 1.0 mg and 0.5 mg for glucose control, and tirzepatide produced greater weight loss at every matched dose level. Choice also depends on formulary coverage, tolerability, and clinical context.

A 2025 JAMA Health Forum simulation of 126 million US adults found tirzepatide would avert more obesity cases (45,609 vs 32,087 per 100,000) and more cardiovascular disease cases (10,655 vs 8,263 per 100,000) than semaglutide over a lifetime, with larger QALY gains (0.35 vs 0.25). However, neither drug was cost-effective at current net prices: the incremental cost-effectiveness ratios were about $197,000/QALY for tirzepatide and $468,000/QALY for semaglutide. Coverage and out-of-pocket cost are often the deciding factors in practice.