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Should I start with tirzepatide or semaglutide as my first peptide?

Updated 2026-05-03

Tirzepatide tends to drive larger weight loss because it works on two hormone pathways instead of one. Semaglutide has a longer real-world track record and the strongest cardiovascular safety data. For pure weight loss with no heart-disease risk factors, most clinicians lean tirzepatide. For patients with cardiovascular history or who want the most studied option, semaglutide is the safer bet. Both are once-weekly injections with similar starter doses and similar early side effects.

IfIf your main goal is the biggest possible weight loss
Thenthen tirzepatide averaged 20.9% loss at 72 weeks in SURMOUNT-1 vs semaglutide''s 14.9% at 68 weeks in STEP 1
IfIf you have known cardiovascular disease or high heart-risk factors
Thenthen semaglutide has the SELECT trial cardiovascular outcomes data behind it
IfIf you have severe nausea on one of them
Thenthen switching to the other is reasonable - some people tolerate tirzepatide better because GIP may blunt nausea
IfIf cost is a hard constraint
Thenthen compounded semaglutide is typically cheaper than compounded tirzepatide on a per-month basis
Key facts
  • Semaglutide is a single GLP-1 receptor agonist; tirzepatide is a dual GIP and GLP-1 agonist
  • SURMOUNT-1 (NCT04184622) showed 20.9% mean weight loss with tirzepatide 15 mg at 72 weeks
  • STEP 1 (NCT03548935) showed 14.9% mean weight loss with semaglutide 2.4 mg at 68 weeks
  • Both follow the same starter pattern: 4 weeks at the lowest dose, then step up monthly
  • Tirzepatide users in head-to-head data are more likely to hit 20%+ weight loss
  • Semaglutide is sold as Wegovy in the US for obesity; tirzepatide is sold as Zepbound
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