Semaglutide vs Tirzepatide: Which Is Right for You?
Both are FDA-approved once-weekly injections for weight management; tirzepatide (Zepbound) acts on GIP and GLP-1 receptors and produced larger average weight loss in its pivotal trial (−20.9% at 15 mg over 72 weeks) than semaglutide 2.4 mg did in STEP 1 (−14.9% over 68 weeks).
Side-by-side comparison
| Semaglutide | Tirzepatide | |
|---|---|---|
| Receptors | GLP-1 | GIP + GLP-1 |
| Brands (weight) | Wegovy, Wegovy HD | Zepbound |
| Maker | Novo Nordisk | Eli Lilly |
| Label max (weight) | 7.2 mg weekly (Wegovy HD) | 15 mg weekly |
| Pivotal trial result | −14.9% at 68 wk (STEP 1, 2.4 mg) | −20.9% at 72 wk (SURMOUNT-1, 15 mg) |
| FDA status | Approved | Approved |
Complete comparison (2026)
Key takeaways
- Different trials, different populations — cross-trial numbers are indicative, not head-to-head.
- Both carry the GLP-1-class boxed thyroid warning.
- Both start low and step up every 4 weeks.
What are Semaglutide and Tirzepatide?
Semaglutide is a long-acting GLP-1 receptor agonist peptide, made by Novo Nordisk, that is FDA-approved for type 2 diabetes (Ozempic, Rybelsus) and for chronic weight management (Wegovy).
Tirzepatide is a once-weekly peptide from Eli Lilly that activates both GIP and GLP-1 receptors; it is FDA-approved as Mounjaro for type 2 diabetes and as Zepbound for chronic weight management and for moderate-to-severe obstructive sleep apnea with obesity.
Mechanism differences
Semaglutide is a pure GLP-1 receptor agonist. Tirzepatide is a single molecule active at both GIP and GLP-1 receptors, which is thought to add to insulin response and appetite reduction.
Effectiveness
STEP 1 reported −14.9% vs −2.4% placebo at 68 weeks with semaglutide 2.4 mg. SURMOUNT-1 reported −15.0%, −19.5% and −20.9% on 5, 10 and 15 mg tirzepatide vs −3.1% placebo at 72 weeks. Wegovy HD 7.2 mg was approved in 2026 on data showing additional weight loss over earlier doses.
Side effect profiles
Similar GI-dominated profiles (nausea, diarrhea, vomiting, constipation). Both labels warn about pancreatitis, gallbladder disease and thyroid C-cell tumors. Altered skin sensation was reported more with semaglutide 7.2 mg.
Dosing & administration
Wegovy: 0.25 mg rising to 2.4 mg over 16 weeks; HD 7.2 mg after 4+ weeks at 2.4 mg. Zepbound: 2.5 mg rising in 2.5 mg steps to a 15 mg maximum. See the linked protocol pages for the label tables.
Cost
Both are brand-only. Cash-pay offers come from the manufacturers' pharmacies and telehealth partners and change often; we link to the live pages rather than quote numbers.
FDA & regulatory status
Both FDA-approved. Compounded versions of either are not FDA-approved.
Who should choose which
The choice is a clinical one made with a prescriber, based on health history, tolerability, coverage and supply. Nothing here is a recommendation.
What the evidence does not show
- A definitive head-to-head ranking from these separate trials.
- That either works the same after stopping.
Frequently asked questions
Is tirzepatide stronger than semaglutide?
In separate pivotal trials, tirzepatide 15 mg produced larger average weight loss (−20.9%) than semaglutide 2.4 mg (−14.9%). Wegovy HD 7.2 mg narrows that gap; direct comparison requires head-to-head trials.
Can semaglutide and tirzepatide be used together?
No. The Zepbound label says it should not be used with any GLP-1 receptor agonist.
Are both FDA-approved?
Yes. Semaglutide as Wegovy/Ozempic/Rybelsus and tirzepatide as Zepbound/Mounjaro.
References
- Once-Weekly Semaglutide in Adults with Overweight or Obesity
- WEGOVY (semaglutide) prescribing information
- FDA Approves Fourth Product Under National Priority Voucher Program, Higher Dose Semaglutide
- Semaglutide — PubChem compound summary (CID 56843331)
- Tirzepatide Once Weekly for the Treatment of Obesity
- ZEPBOUND (tirzepatide) prescribing information
- Tirzepatide — PubChem compound summary (CID 166567236)
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