Mounjaro vs Zepbound: the same drug under two names

Mounjaro versus Zepbound is the simplest comparison in the GLP-1 world, because there’s only one drug in the room. Both are tirzepatide, the dual GIP/GLP-1 agonist made by Eli Lilly — identical molecule, identical strengths. The only real difference is the label on the box and what it’s approved to treat.

Same molecule, two approved uses

Mounjaro is tirzepatide approved for type-2 diabetes. Zepbound is the same tirzepatide approved for chronic weight management (and, separately, for moderate-to-severe obstructive sleep apnea in adults with obesity). This is the same brand-splitting Novo Nordisk does with semaglutide — Ozempic for diabetes, Wegovy for weight — and it’s done largely for regulatory and insurance reasons, not because the pills differ.

The weight-loss numbers

Because it’s the same molecule, the efficacy is the same. In SURMOUNT-1, the pivotal obesity trial (the Zepbound indication), tirzepatide produced mean weight loss of 15.0%, 19.5% and 20.9% at the 5, 10 and 15 mg doses over 72 weeks — versus 3.1% on placebo.^[1]In SURPASS-2, the diabetes trial (the Mounjaro setting), weight loss is a secondary benefit but still substantial, beating injectable semaglutide by up to 5.5 kg.^[2] Whether you call it Mounjaro or Zepbound, the drug does the same thing.

The honest verdict

There is no “better” between Mounjaro and Zepbound — they are the same tirzepatide at the same doses with the same effects.^[1] The choice is made for you by your diagnosis and your plan’s coverage, not by any property of the drug. If your real question is how tirzepatide compares with semaglutide, see Zepbound vs Wegovyand Mounjaro vs Ozempic; for routes to a prescription, our GLP-1 provider guide.