Semaglutide vs tirzepatide
Both medications are once-weekly GLP-1-class injectables. They share a mechanism but differ in important ways. Here is what the evidence shows.
At a glance
| Feature | Semaglutide | Tirzepatide |
|---|---|---|
| Drug class | GLP-1 receptor agonist | Dual GIP + GLP-1 receptor agonist |
| Brand-name versions | Ozempic, Wegovy | Mounjaro, Zepbound |
| Administration | Once-weekly injection | Once-weekly injection |
| Average weight loss (clinical trial, full dose) | ~14.9% of body weight at 68 weeks | ~20.9% of body weight at 72 weeks |
| Typical max therapeutic dose | 2.4 mg | 15 mg |
| Side effect profile | Mostly GI; tolerable for most | Similar GI profile; some report fewer cravings at lower nausea |
| Who it is best for | Most people starting GLP-1 therapy | People who want stronger results or have plateaued on semaglutide |
Mechanism of action
Semaglutide activates only the GLP-1 receptor. Tirzepatide activates both GLP-1 and GIP receptors. The dual mechanism is associated with greater appetite reduction and metabolic improvement in clinical trials, though individual response varies — some people lose more on semaglutide and tolerate it better.
Clinical results compared
The most direct comparison comes from SURPASS-2 (a head-to-head trial in people with type 2 diabetes), where tirzepatide produced significantly greater weight loss than semaglutide at all comparable doses. The dedicated obesity trials (STEP for semaglutide, SURMOUNT for tirzepatide) reinforce that pattern in non-diabetic populations.
Side effects
Both medications cause GI side effects — most commonly nausea, constipation, or diarrhea — that ease as the body adjusts. Tirzepatide users sometimes report stronger appetite reduction with similar nausea levels. Both share a boxed warning for medullary thyroid carcinoma and similar contraindications.
How to choose
Most members start on semaglutide for three reasons: cost is lower, the safety record is the longest, and average results are clinically meaningful. Members typically consider tirzepatide when they:
- Want maximum weight loss in the shortest timeframe
- Have plateaued on semaglutide
- Have a BMI ≥35 with multiple weight-related conditions
Your clinician will recommend the option that fits your medical history, goals, and tolerability.
Frequently asked questions
Can I switch between the two medications?
Which has fewer side effects?
Are they both compounded by the same pharmacies?
Ready when you are.
Take a 90-second medical intake. Your clinician reviews it and prescribes only when clinically appropriate.
See treatment plans →Related reading
References & sources
- Frías JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. NEJM. 2021;385:503–515.
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. NEJM. 2021;384:989–1002.
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity. NEJM. 2022;387:205–216.
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This educational content follows WeightlessRx clinical content standards and is reviewed for accuracy against current obesity-medicine and GLP-1 treatment guidelines, including FDA prescribing information, the American Association of Clinical Endocrinology (AACE) obesity guideline, and peer-reviewed clinical literature. Information is educational and is not medical advice. Treatment eligibility is determined only after a U.S.-licensed clinician in our third-party provider network reviews your intake and medical history. Read our full medical review policy →