Head-to-head weight loss
From the only large trial that directly compared these two drugs. 751 adults with obesity, 72 weeks at maximum dose.
That is the headline number. But neither drug is universally "better" — they differ on heart evidence, cost, and form. Here is the fuller picture.
Weight loss at maximum approved dose
Including the oral semaglutide pill, which was not part of the head-to-head trial.
Monthly cost
The oral pill option is cheaper than either injection's self-pay price.
Side effects comparison
From each drug's main weight loss trial. All stomach side effects are most common in the first 4–8 weeks and usually fade.
Beyond weight loss
Heart protection
- Semaglutide — 20% reduction in major heart events — proven in a large 17,604-person trial
- Tirzepatide — Heart safety confirmed — heart benefit trial in progress
Form & convenience
- Tirzepatide — Weekly injection only — no food timing restrictions
- Semaglutide — Weekly injection OR daily pill — pill needs 30-min fasting window
Side effects
- Nausea (semaglutide)44%
- Nausea (tirzepatide)31%
- Quit due to side effects~7%
Usually peaks weeks 2–4, fades by week 8–12
Prefer a pill over injections?
Two oral GLP-1 pills are now FDA-approved: Oral Wegovy (~16.6% weight loss, from $149/month) and Foundayo (~12.4% weight loss, no food restrictions).
Common questions
Written and maintained by one person · Built with agentic AI tools · Every number checked against the cited trial · Not medical advice
The numbers above come from the following clinical trials.
- SURMOUNT-5 (head-to-head): 751 adults with obesity, 72 weeks. Tirzepatide 20.2% vs semaglutide 13.7% average weight loss. Published 2025.
- SURMOUNT-1 (tirzepatide): 2,539 participants, 72 weeks. 20.9% average weight loss at 15mg dose.
- STEP 1 (semaglutide injection): 1,961 participants, 68 weeks. 14.9% average weight loss at 2.4mg dose.
- OASIS 4 (oral semaglutide): 307 participants, 68 weeks. 16.6% weight loss with full adherence.
- SELECT (semaglutide heart study): 17,604 adults without diabetes, 3+ years. 20% reduction in major heart events.
- SURPASS-CVOT (tirzepatide heart study): Shown to be at least as safe for the heart as dulaglutide.
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