Semaglutide vs Tirzepatide
The two most effective approved weight-loss and diabetes drugs, compared on mechanism, trial results, cardiovascular evidence, and safety.
In head-to-head diabetes trials and cross-trial obesity data, tirzepatide produces larger average weight loss and HbA1c reduction. Semaglutide has the more mature cardiovascular-outcomes evidence in people without diabetes. Both are FDA-approved and share the GLP-1 class safety profile.
| Semaglutide | Tirzepatide | |
|---|---|---|
| Mechanism | GLP-1 receptor agonist | Dual GIP + GLP-1 receptor agonist |
| Regulatory status | FDA-approved (Ozempic, Wegovy, Rybelsus) | FDA-approved (Mounjaro, Zepbound) |
| Approved for | Type 2 diabetes, weight management, cardiovascular risk reduction | Type 2 diabetes, weight management, obstructive sleep apnea |
| Mean weight loss (trial) | ~15% at 68 wks on 2.4 mg (STEP 1) | Up to ~21% at 72 wks on 15 mg (SURMOUNT-1) |
| Head-to-head in diabetes | Comparator arm | Greater HbA1c and weight reduction (SURPASS-2) |
| Cardiovascular evidence | Grade A — MACE reduction in obesity without diabetes (SELECT) and in T2D (SUSTAIN-6) | Grade C — dedicated CV outcomes trial (SURPASS-CVOT) ongoing |
| Dosing | Weekly injection or daily oral tablet | Weekly injection |
| Half-life | ~7 days | ~5 days |
| Common side effects | Nausea, vomiting, diarrhea, constipation | Nausea, diarrhea, vomiting, constipation |
| Boxed warning | Thyroid C-cell tumors (rodent data) | Thyroid C-cell tumors (rodent data) |
How to read this comparison
These are the two most effective incretin drugs approved to date, and the honest answer to “which is better” depends on the outcome you care about.
For weight loss and glycemic control, the evidence favors tirzepatide on the numbers. In SURPASS-2 — the only large head-to-head in type 2 diabetes — tirzepatide beat semaglutide 1 mg on both HbA1c and weight. Cross-trial, the obesity programs (SURMOUNT-1 vs STEP 1) point the same direction, though cross-trial comparisons are weaker than a direct one.
For cardiovascular protection, semaglutide currently has the stronger hand. SELECT showed a 20% reduction in major cardiovascular events in people with obesity but without diabetes — a landmark result — and SUSTAIN-6 established benefit in type 2 diabetes. Tirzepatide’s dedicated cardiovascular-outcomes trial has not yet reported, so its CV benefit is biologically plausible but not yet proven on hard endpoints.
On safety, the two are more alike than different: a gastrointestinal-dominant side-effect profile that eases with slow titration, the same rodent-based thyroid boxed warning, and the same contraindications.
Neither of these is a decision you make from a web page. Both are prescription medications, and which one fits — if either does — is a conversation with a clinician who knows your history.
A note on "dose"
Any doses shown here are the amounts studied in trialsor the approved label schedule — not a recommendation, and not the same thing as a dose someone reports using online. See how we separate dose language.
References