Semaglutide vs tirzepatide: how they compare
Both are once-weekly injectables for weight management. Semaglutide activates one hormone receptor (GLP-1); tirzepatide activates two (GIP and GLP-1). In trials, tirzepatide produced greater average weight loss, but the right choice depends on your health history, tolerance, and goals — a licensed provider decides.
How each medication works
Semaglutide is a GLP-1 receptor agonist: it mimics glucagon-like peptide-1, a gut hormone that signals fullness, slows how quickly the stomach empties, and helps regulate blood sugar. It is the active ingredient in the FDA-approved brands Wegovy (for chronic weight management) and Ozempic (for type 2 diabetes).
Tirzepatide is a dual GIP and GLP-1 receptor agonist: it acts on the same GLP-1 pathway plus a second gut hormone, glucose-dependent insulinotropic polypeptide (GIP). Engaging both receptors is thought to enhance appetite regulation and metabolic effects. It is the active ingredient in the FDA-approved brands Zepbound (for chronic weight management) and Mounjaro (for type 2 diabetes).
Side-by-side: the key differences
The two medications share a class and a delivery method but differ in their targets and, on average, their results and tolerability.
- Mechanism: semaglutide targets GLP-1 only; tirzepatide targets both GIP and GLP-1.
- Formulation: both are once-weekly subcutaneous injections; semaglutide (Ozempic/Wegovy) also has an oral tablet form, while tirzepatide is injection-only.
- Average weight loss in trials: in STEP-1, adults on semaglutide 2.4 mg lost about 14.9% of body weight over 68 weeks vs 2.4% on placebo. In SURMOUNT-1, adults on tirzepatide lost about 15%, 19.5%, and 20.9% at the 5 mg, 10 mg, and 15 mg doses over 72 weeks vs 3.1% on placebo.
- Head-to-head: the SURMOUNT-5 trial (2025) directly compared the two in adults with obesity and reported greater average weight loss with tirzepatide than with semaglutide.
- Side-effect profile: both cause primarily gastrointestinal effects (nausea, diarrhea, vomiting, constipation); profiles are broadly similar, and individual tolerance varies.
- Note: trial percentages come from specific brand-name studies and describe averages — they are not a promise of individual results, and compounded versions are not the FDA-approved products studied in these trials.
How a provider chooses between them
A greater average result in a trial does not automatically make one medication the right choice for you. A licensed provider weighs your medical history, current medications, prior response to GLP-1 therapy, side-effect tolerance, and personal treatment goals. They also review contraindications — including a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), for which both classes carry a boxed warning.
Availability, insurance coverage, and cost also factor into the decision. The takeaway: these are prescription medications with real risks and benefits, and a licensed provider determines which is right for you.
Is tirzepatide better than semaglutide?
In clinical trials, including the head-to-head SURMOUNT-5 study (2025), tirzepatide produced greater average weight loss than semaglutide. But 'better' depends on the individual — tolerance, health history, and goals all matter. A licensed provider determines which is right for you.
Are the side effects different?
Both medications cause mainly gastrointestinal effects — nausea, vomiting, diarrhea, and constipation — that are usually mild to moderate and often ease as the dose is gradually increased. The profiles are broadly similar, though individual tolerance varies. Both carry the same class warnings and contraindications.
Can I switch from one to the other?
Some people switch between GLP-1 medications for reasons such as tolerability, response, or availability, but this should only be done under the guidance of a licensed provider, who will manage dosing and titration to reduce side effects. Do not switch or adjust doses on your own.
Are both taken the same way?
Both are once-weekly subcutaneous injections. Semaglutide (as Ozempic/Wegovy) is also available in an oral tablet form, while tirzepatide is injection-only. Your provider will explain the specific product, dose, and titration schedule prescribed for you.
Do the trial results guarantee how much I'll lose?
No. Trial percentages such as those from STEP-1 and SURMOUNT-1 are averages measured under study conditions, usually alongside lifestyle changes. Individual results vary based on many factors. These figures describe the FDA-approved products studied, not compounded versions.