Ozempic vs Mounjaro vs Zepbound Calculator
Compare projected weight loss across all three GLP-1 medications side by side
Medical Disclaimer: This tool provides general educational estimates. Always consult your prescribing physician or healthcare provider before making medication changes or interpreting results from population-based models.
Frequently Asked Questions
In clinical trials, tirzepatide (Mounjaro/Zepbound) at 15 mg produced 22.5% body weight loss over 72 weeks (SURMOUNT-1), compared to semaglutide (Ozempic/Wegovy) at 2.4 mg which produced 14.9% over 68 weeks (STEP-1). However, individual results vary widely, and no head-to-head trial at maximum weight-loss doses exists.
Mounjaro and Zepbound are the same drug (tirzepatide) by Eli Lilly. The only difference is the FDA-approved indication: Mounjaro for type 2 diabetes, Zepbound for chronic weight management. Weight loss efficacy is identical.
GLP-1 receptor agonists mimic the incretin hormone GLP-1, which slows gastric emptying, reduces appetite, and increases satiety. Tirzepatide also activates GIP receptors, enhancing insulin secretion and fat metabolism.
Most people notice weight loss within 4-8 weeks. Semaglutide shows the most rapid loss between weeks 12-28. Tirzepatide continues producing meaningful loss further into treatment, with the steepest decline between weeks 12-36.
Yes. Ozempic projections use STEP-1 (Wilding et al., NEJM 2021, N=1,961). Mounjaro/Zepbound projections use SURMOUNT-1 (Jastreboff et al., NEJM 2022, N=2,539). Weight loss curves are modeled as non-linear, reflecting clinical trial patterns.
Sources
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002. Link
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med. 2022;387(3):205-216. Link
- Frias JP, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). N Engl J Med. 2021;385(6):503-515. Link
- FDA Approves New Medication for Chronic Weight Management (Zepbound). FDA News Release, November 2023. Link
Methodology
This calculator projects weight loss for three GLP-1 medications using mean percentage weight loss data from two landmark clinical trials. Ozempic/Wegovy projections are based on STEP-1 (Wilding et al., NEJM 2021; N=1,961) reporting 14.9% mean body weight loss at 68 weeks. Mounjaro/Zepbound projections are based on SURMOUNT-1 (Jastreboff et al., NEJM 2022; N=2,539) reporting 22.5% at 72 weeks. Weight loss curves use a saturating exponential model reflecting the observed non-linear trajectory.
Cross-trial comparisons are approximate because the trials enrolled different patient populations with different protocols. Individual results vary significantly.
GLP-1 comparison: Ozempic (semaglutide 2.4 mg) produced 14.9% weight loss at 68 weeks (STEP-1). Mounjaro/Zepbound (tirzepatide 15 mg) produced 22.5% at 72 weeks (SURMOUNT-1). Mounjaro and Zepbound are the same drug with different indications. Tirzepatide targets GLP-1 + GIP; semaglutide targets GLP-1 only.
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