How Do Zepbound and Wegovy Work?
Zepbound (tirzepatide) activates both GLP-1 and GIP receptors to suppress appetite and regulate blood sugar. Wegovy (semaglutide) targets only the GLP-1 receptor for similar effects. Tirzepatide's dual action often leads to greater weight loss in trials.[1]
What Do Clinical Trials Show for Weight Loss?
In head-to-head data from SURMOUNT-5, Zepbound caused 20.2% average weight loss over 72 weeks, versus 13.7% for Wegovy—a 47% relative improvement.[2] Earlier SURMOUNT trials showed tirzepatide at 15-22% loss; STEP trials for semaglutide at 12-18%.[1][3] Both reduce cardiovascular risk, but Zepbound edges out on average reductions.
Which Is Better for Diabetes Control?
Zepbound, branded as Mounjaro for type 2 diabetes, lowers A1C more effectively (up to 2.3% drop) than Wegovy (1.6-1.9%), per SURPASS and SUSTAIN studies.[1][4] If diabetes is a factor, Zepbound has stronger data.
Side Effects and Safety Comparison
Both cause nausea, diarrhea, and vomiting, peaking early then fading. Zepbound reports slightly higher GI issues due to dual agonism, but similar dropout rates. Rare risks like pancreatitis or thyroid tumors apply to both; no major safety gaps in trials.[1][2] Long-term data favors semaglutide (longer market history).
| Aspect | Zepbound (Tirzepatide) | Wegovy (Semaglutide) |
|-----------------|------------------------|----------------------|
| Max Dose | 15 mg weekly | 2.4 mg weekly |
| Weight Loss (avg) | 20%+ | 15% |
| A1C Reduction | 2.3% | 1.9% |
| Common Sides | Nausea (35%), diarrhea| Nausea (44%), vomit |
| Approval Year | 2023 (obesity) | 2021 (obesity) |
Cost and Availability Breakdown
Wegovy lists at $1,349/month; Zepbound at $1,060—about 20% cheaper without insurance.[5] Both face shortages. Manufacturer coupons cut copays to $25/month for eligible patients. Insurance covers Wegovy more often for heart risk; Zepbound gaining traction.
Who Might Prefer One Over the Other?
Zepbound suits max weight loss or diabetes needs. Wegovy fits if cardiac protection is priority (proven in SELECT trial) or for established tolerability. Real-world adherence similar; switch if one fails response.[1][6] Consult a doctor—individual factors like BMI, comorbidities decide.
[1] NEJM: Tirzepatide vs Semaglutide Trials (https://www.nejm.org/doi/full/10.1056/NEJMoa2302392)
[2] Lilly SURMOUNT-5 Results (https://investor.lilly.com/news-releases/news-release-details/lillys-zepboundr-tirzepatide-superior-wegovyr-semaglutide-head)
[3] Novo Nordisk STEP Program (https://www.nejm.org/doi/full/10.1056/NEJMoa2032183)
[4] ADA Guidelines on GLP-1s (https://diabetesjournals.org/care/issue/47/Supplement_1)
[5] GoodRx Pricing (https://www.goodrx.com/compare/zepbound-vs-wegovy)
[6] JAMA Real-World Analysis (https://jamanetwork.com/journals/jama/fullarticle/2820130)