Semaglutide vs Tirzepatide: What the Evidence Shows
Tirzepatide produced larger weight loss in trials, including the head-to-head SURMOUNT-5 (20.2% vs 13.7%); semaglutide has the longer cardiovascular-outcomes record and a daily pill for weight loss. An independent, evidence-based comparison.
Medically reviewed by Dr. Jonathan Snipes, MD
Reviewed for clinical accuracy · Last reviewed September 23, 2026 · Review policy
Quick answer
For weight loss, tirzepatide produced larger average loss in trials, including a head-to-head trial (SURMOUNT-5: 20.2% versus 13.7% for semaglutide at 72 weeks), while semaglutide has the longer cardiovascular-outcomes track record and a daily pill option for weight loss (Wegovy pill). Both are FDA-approved and Grade A; the better choice depends on the goal, tolerability, and cost, and is a clinician's decision.
| Semaglutide | Tirzepatide | |
|---|---|---|
| Mechanism | GLP-1 receptor agonist | Dual GIP + GLP-1 receptor agonist |
| Avg weight loss (trials) | ~15% (STEP 1, 2.4 mg, 68 weeks); 13.7% head-to-head (SURMOUNT-5) | Up to ~21% (SURMOUNT-1, 15 mg, 72 weeks); 20.2% head-to-head (SURMOUNT-5) |
| Also approved for | Type 2 diabetes; CV risk reduction (with or without diabetes); kidney disease in type 2 diabetes; MASH with liver fibrosis | Type 2 diabetes; CV risk reduction in type 2 diabetes; obstructive sleep apnea with obesity |
| Formulations | Weekly injection (Ozempic, Wegovy); daily tablet for weight (Wegovy pill) and for diabetes (Rybelsus) | Weekly injection |
| Tolerability | Mostly GI; thyroid C-cell boxed warning | Mostly GI; thyroid C-cell boxed warning |
| Brand names | Ozempic, Wegovy, Rybelsus | Mounjaro, Zepbound |
Weight loss: tirzepatide leads
In their pivotal placebo-controlled trials, tirzepatide produced up to about 21% average weight loss at the 15 mg dose over 72 weeks (SURMOUNT-1), versus about 15% for semaglutide 2.4 mg over 68 weeks (STEP 1). The two drugs have also been tested directly against each other: in SURMOUNT-5, a 72-week head-to-head trial in adults with obesity and without diabetes, tirzepatide produced 20.2% average weight loss versus 13.7% for semaglutide. Individual results vary, but tirzepatide is generally considered the more powerful weight-loss agent. Its dual action on both the GIP and GLP-1 receptors is the leading explanation.
These figures are at the highest trial doses (tirzepatide 15 mg, semaglutide 2.4 mg), reached only after several months of gradual dose increases. Lower doses produce less weight loss. Dose and pace are set by a prescriber.
Where semaglutide counters
Semaglutide keeps two advantages. First, it is the only one of the two proven to reduce heart attacks, strokes and cardiovascular death in people with overweight or obesity and heart disease who do not have diabetes (SELECT). Tirzepatide gained its own cardiovascular indication in August 2026, but only for adults with type 2 diabetes (SURPASS-CVOT). Second, semaglutide comes as a once-daily pill for weight loss (the Wegovy pill, approved December 2025), which matters for anyone reluctant to inject; Rybelsus, the older semaglutide tablet, is approved for type 2 diabetes, not weight loss. Tirzepatide, in turn, is FDA-approved for obstructive sleep apnea, an indication semaglutide does not hold.
Tolerability is similar
Both are titrated slowly to manage gastrointestinal side effects, which are the most common complaint for each. Both carry the same boxed warning for thyroid C-cell tumors seen in rodents and are contraindicated in people with a personal or family history of medullary thyroid carcinoma or MEN 2. Neither is a clear winner on safety.
Compounded versions are not the same drugs
Compounded semaglutide and tirzepatide are not FDA-approved. Both came off the FDA shortage list (tirzepatide December 2024, semaglutide February 2025), which ended the shortage exception for mass compounding, and a federal appeals court upheld those decisions in August 2026. See our news coverage for current status.
Bottom line
Tirzepatide edges out semaglutide on raw weight loss in the trial data, including a head-to-head trial. Semaglutide counters with proven cardiovascular risk reduction in people without diabetes (SELECT) and a daily pill option for weight loss (Wegovy pill). Both are Grade A, FDA-approved, and prescription-only, so the right pick is individual, not universal.
Frequently asked questions
Is tirzepatide better than semaglutide for weight loss?+
Yes, on average. In the head-to-head SURMOUNT-5 trial, tirzepatide produced 20.2% average weight loss versus 13.7% for semaglutide over 72 weeks. Results vary, and semaglutide still has advantages, including a cardiovascular benefit proven in people without diabetes and a once-daily pill option for weight loss.
Which has fewer side effects, semaglutide or tirzepatide?+
Their side-effect profiles are similar, mostly gastrointestinal, and both carry the same thyroid boxed warning. Neither is clearly better tolerated.
Can you switch from semaglutide to tirzepatide?+
Switching is common and is done under clinician supervision with re-titration. This is a medical decision based on response, tolerability, and access, not something to self-manage.
Sources
- 1.Drugs@FDA: FDA-Approved Drugs database · U.S. Food & Drug Administration
- 2.Jastreboff AM et al. Tirzepatide Once Weekly for Obesity (SURMOUNT-1), NEJM 2022 · New England Journal of Medicine
- 3.Wilding JPH et al. Once-Weekly Semaglutide in Overweight or Obesity (STEP 1), NEJM 2021 · New England Journal of Medicine
- 4.Aronne LJ et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity (SURMOUNT-5), NEJM 2025 · New England Journal of Medicine
- 5.Lincoff AM et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT), NEJM 2023 · PubMed / New England Journal of Medicine
- 6.FDA approves Novo Nordisk's Wegovy pill for weight loss (December 22, 2025) · Novo Nordisk via PR Newswire
- 7.FDA approves Lilly's Mounjaro to reduce cardiovascular risk in adults with type 2 diabetes (SURPASS-CVOT, August 28, 2026) · Eli Lilly via PR Newswire
- 8.FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize · U.S. Food & Drug Administration