Short answer
Same molecule, different label. Both are tirzepatide, made by Eli Lilly and injected weekly. Zepbound is FDA-approved for weight management and for obstructive sleep apnea with obesity. Mounjaro is approved for type 2 diabetes and, since August 2026, for reducing heart risk in people with type 2 diabetes. The dose steps and pens are the same; the approved uses are not.
One drug, two approvals
Tirzepatide activates two gut-hormone receptors, GIP and GLP-1. Lilly sells it under two names because the FDA approves drugs by indication. Mounjaro was approved in May 2022 for type 2 diabetes. Zepbound followed in November 2023 for chronic weight management, and in December 2024 it added moderate to severe obstructive sleep apnea in adults with obesity. On 28 August 2026 Mounjaro gained a further indication: reducing cardiovascular risk in adults with type 2 diabetes, based on the SURPASS-CVOT trial.
Same dosing schedule
Both labels start at 2.5 mg once a week for four weeks, then 5 mg, with increases of 2.5 mg after at least four weeks at each step and a maximum of 15 mg. Both come in single-dose pens and a KwikPen; Zepbound also comes in vials. The label’s missed-dose rule is the same too: take it within four days, otherwise skip. Your prescriber decides which product and which dose.
Why the name on the box matters
Insurance and price. Plans that cover diabetes drugs may cover Mounjaro but not weight-loss drugs, and the reverse. Medicare’s GLP-1 Bridge, which started on 1 July 2026, covers Zepbound for eligible members at a $50 copay. Lilly’s self-pay price for Zepbound through LillyDirect runs from $299 to $449 a month depending on dose. Using Mounjaro for weight alone is off-label, and that is a conversation for your prescriber.
Related questions
Can I switch between them?
Only a prescriber can decide that. The molecule is the same, so the change is about indication, coverage and price, not chemistry.
Is Zepbound a peptide?
Yes. Tirzepatide is a peptide medicine, which is why it is injected. Lilly’s pill, Foundayo, is a different, non-peptide molecule.
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Published 2026-09-30 · Last checked 2026-09-30
Educational content, not medical advice. Made for the United States.