Zepbound (tirzepatide) is the FDA-approved-for-weight-loss version of the same dual GIP/GLP-1 medication sold as Mounjaro. Approved for chronic weight management in late 2023, it has delivered some of the highest average weight loss results recorded for a medication. Use our free calculator to estimate your trajectory from the SURMOUNT-1 clinical trial.
Zepbound's weight loss data comes from the SURMOUNT-1 trial — a 72-week study of 2,539 adults with obesity (without diabetes), published in the New England Journal of Medicine in 2022.
Source: Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022;387(3):205-216. PMID: 35658024
For someone starting at 250 lbs, a 22.5% reduction is about 56 lbs over roughly 17 months at the top dose. Because Zepbound and Mounjaro are the same medication, the projections are interchangeable.
Zepbound uses the same step-up schedule as Mounjaro to limit GI side effects:
| Weeks | Weekly Dose | Phase |
|---|---|---|
| 1–4 | 2.5 mg | Starting dose (tolerance) |
| 5–8 | 5 mg | First maintenance dose |
| 9–12 | 7.5 mg | Step-up |
| 13–16 | 10 mg | Maintenance or step-up |
| 17–20 | 12.5 mg | Step-up |
| 21+ | 15 mg | Maximum dose |
Converting a dose into pen units? Use the GLP-1 dose calculator.
Yes — Zepbound and Mounjaro both contain tirzepatide at the same doses (2.5 mg to 15 mg weekly). The difference is the FDA-approved use: Zepbound is approved for chronic weight management in adults with obesity or overweight, while Mounjaro is approved for type 2 diabetes. Clinically the molecule and expected weight loss are identical.
In the SURMOUNT-1 trial, adults on tirzepatide 15 mg lost an average of 22.5% of their body weight over 72 weeks, with 10 mg around 19.5% and 5 mg around 15%. About one third of those on the highest dose lost 25% or more. Individual results depend on starting weight, the dose you tolerate, diet, and activity.
Head-to-head, tirzepatide has outperformed semaglutide. The SURMOUNT-5 trial directly compared Zepbound and Wegovy and found greater average weight loss with Zepbound (roughly 20% vs 14%). Both are highly effective; Zepbound's dual GIP/GLP-1 action appears to give it an edge for many people.
Because Zepbound is FDA-approved specifically for weight management, more insurance plans cover it for obesity than cover off-label use of diabetes drugs — though coverage still varies widely by plan and often requires prior authorization and a qualifying BMI. Check your formulary and ask your provider about savings programs.
Our free calculator uses SURMOUNT-1 trial data to project your personalized week-by-week weight loss timeline.
Try Our Full GLP-1 Weight Loss CalculatorThis calculator is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Weight loss projections are estimates based on average clinical trial results and may not reflect your individual experience. Zepbound (tirzepatide) is a prescription medication that should only be used under the supervision of a qualified healthcare provider. Always consult your doctor before starting, stopping, or changing any medication.