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.
Tirzepatide
Tirzepatide
Identical molecule (tirzepatide). Different FDA indications — Mounjaro for type 2 diabetes, Zepbound for obesity (and OSA in obesity, added Dec 2024). The choice between them is which one your insurance covers for your diagnosis. LillyDirect launched cash-pay vials of Zepbound in 2024 at $399–$549, which changed the cash-pay calculus.
Molecule
MounjaroTirzepatide
ZepboundTirzepatide
Receptor(s)
MounjaroGIP + GLP-1 (dual agonist)
ZepboundGIP + GLP-1 (dual agonist)
Manufacturer
MounjaroEli Lilly
ZepboundEli Lilly
FDA approval
MounjaroMay 2022
ZepboundNovember 2023 (obesity); December 2024 (obstructive sleep apnea in obesity)
Indication
MounjaroType 2 diabetes (with HFpEF and OSA indications added 2024)
ZepboundChronic weight management; OSA in adults with obesity (added Dec 2024)
Delivery
MounjaroSubcutaneous injection, once weekly
ZepboundSubcutaneous injection, once weekly
Dose ceiling
Mounjaro15 mg weekly
Zepbound15 mg weekly
Titration
Mounjaro4 weeks per step
Zepbound4 weeks per step
Typical loss
Mounjaro~9–13% body weight at 1 year in T2D patients (SURPASS), ~22% off-label in non-diabetics at 15 mg
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
Mounjaro$1,070–$1,180 list
Zepbound$1,060 list; $499–$649 via LillyDirect self-pay vials (2024+)
On patent until
Mounjaro2036 (US composition of matter; formulation patents to ~2039)
Zepbound2036 (US)