Both are GLP-1 receptor agonists. Beyond that they differ in molecule, FDA indication, dose ceiling, and — most importantly to most people reading this — what the scale actually does over the long run.
Semaglutide
Tirzepatide
Both are FDA-approved for obesity. Tirzepatide produced ~50% more mean weight loss than semaglutide in the first head-to-head trial (SURMOUNT-5, 2024). Coverage and tolerability are the practical tiebreakers — some people respond better to one molecule than the other, and you only learn which by trying.
Molecule
WegovySemaglutide
ZepboundTirzepatide
Receptor(s)
WegovyGLP-1
ZepboundGIP + GLP-1 (dual agonist)
Manufacturer
WegovyNovo Nordisk
ZepboundEli Lilly
FDA approval
WegovyJune 2021 (obesity); March 2024 (cardiovascular risk reduction)
ZepboundNovember 2023 (obesity); December 2024 (obstructive sleep apnea in obesity)
Indication
WegovyChronic weight management in adults with BMI ≥30, or ≥27 with comorbidity; cardiovascular risk reduction
ZepboundChronic weight management; OSA in adults with obesity (added Dec 2024)
Delivery
WegovySubcutaneous injection, once weekly
ZepboundSubcutaneous injection, once weekly
Dose ceiling
Wegovy2.4 mg weekly
Zepbound15 mg weekly
Titration
Wegovy4 weeks per step (16 weeks to maintenance)
Zepbound4 weeks per step
Typical loss
Wegovy~14.9% mean body weight at 68 weeks in STEP-1 (vs 2.4% placebo); ~17% in adolescents (STEP TEENS)
Zepbound~20.9% mean body weight at 72 weeks in SURMOUNT-1 (15 mg arm) vs. 3.1% placebo; ~26.6% in SURMOUNT-3 (with intensive lifestyle); ~23% in SURMOUNT-5 head-to-head vs. semaglutide (vs. ~15%)
Cash list
Wegovy$1,350 list (often $0–$25 with commercial coverage)
Zepbound$1,060 list; $499–$649 via LillyDirect self-pay vials (2024+)
On patent until
Wegovy2031 (US composition of matter)
Zepbound2036 (US)