Mounjaro and Zepbound are the same drug, tirzepatide, in the same 2.5 to 15 mg weekly doses. Mounjaro is approved for type 2 diabetes; Zepbound for weight management and obesity-related sleep apnea. In SURMOUNT-1, the 15 mg dose cut weight by 20.9% vs 3.1% on placebo. Self-pay, Zepbound costs $299 to $449 a month; Mounjaro $499.
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 in adults and children 10 and older, and to reduce the risk of heart attack, stroke and cardiovascular death in adults with type 2 diabetes at high cardiovascular risk.[3] Zepbound is the same tirzepatide approved for chronic weight management (and, separately, for moderate-to-severe obstructive sleep apnea in adults with obesity, an approval the FDA granted in December 2024 on the strength of the SURMOUNT-OSA trials). 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 injections differ.[4] Both brands come in the same strengths and the same devices: single-dose pens, single-dose vials, multi-dose vials and the four-dose KwikPen.[3][4]
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.
- Tirzepatide 5 mg15%
- Tirzepatide 10 mg19.5%
- Tirzepatide 15 mg20.9%
| Mounjaro | Zepbound | |
|---|---|---|
| Molecule | Tirzepatide | Tirzepatide (identical) |
| Approved for | Type 2 diabetes (adults, children 10+); CV risk reduction in type 2 diabetes | Weight management; OSA with obesity (adults) |
| Mechanism | GIP + GLP-1 | GIP + GLP-1 (same) |
| Doses | 2.5 to 15 mg/week | 2.5 to 15 mg/week (same) |
| Weight loss | Substantial (secondary) | Up to ~20.9% (primary) |
| Self-pay (LillyDirect) | $499/month, any dose | $299 to $449/month by dose |
| Maker | Eli Lilly | Eli Lilly |
Which one costs less without insurance?
Usually Zepbound. As of October 2026, LillyDirect sells Zepbound vials or KwikPens for $299 (2.5 mg), $399 (5 mg) and $449 (7.5 to 15 mg) a month, as long as you refill within 45 days; miss that window and the higher doses cost $499 (7.5 mg) or $699 (10 to 15 mg).[5] Mounjaro pens cost $499 a month at every dose.[6] With commercial insurance that covers the drug, either savings card can cut the copay to as little as $25. Medicare’s GLP-1 Bridge ($50 a month) covers the Zepbound KwikPen for weight management; it excludes people with type 2 diabetes.[7]
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.