Wegovy vs Zepbound: Which Weight-Loss Injection Is Better?
This is the comparison that actually matters for weight loss — and for the first time, we have head-to-head trial data.
Wegovy (semaglutide) and Zepbound (tirzepatide) are the two heavyweight weight-loss injections. They're different molecules — and a direct head-to-head trial gave tirzepatide the edge.
The core difference: single vs dual action
Wegovy's semaglutide is a single agonist — it targets one hormone receptor (GLP-1). Zepbound's tirzepatide is a dual agonist — it targets two (GIP and GLP-1). In simple terms, tirzepatide pulls two appetite-and-metabolism levers instead of one.
The head-to-head data (SURMOUNT-5)
For years the comparison relied on separate trials. Then SURMOUNT-5, a direct head-to-head study published in The New England Journal of Medicine in May 2025, compared the two in adults with obesity:
| Outcome (72 weeks) | Zepbound (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Average body-weight loss | ~20.2% | ~13.7% |
| Achieved ≥25% weight loss | ~31.6% | ~16.1% |
In that trial, tirzepatide produced meaningfully greater weight loss than semaglutide. Broader single-drug trials point the same direction: semaglutide 2.4mg averaged roughly 15% in its pivotal STEP trials, while tirzepatide reached roughly 20–22% at its top dose in SURMOUNT-1.
Does that mean Zepbound is always the winner?
Not necessarily for every person. Averages aren't individuals — some people respond beautifully to semaglutide, tolerate it better, or can access it more affordably. But if raw weight-loss potential is the question, current evidence favors tirzepatide.
Side effects
Both cause similar side effects, mostly gastrointestinal — nausea, vomiting, diarrhea, and constipation — which usually ease as your body adjusts and as the dose is raised slowly. Both carry a boxed warning about thyroid C-cell tumors and are not for people with a personal or family history of medullary thyroid carcinoma or MEN2. Serious risks include pancreatitis and gallbladder problems.
How to think about choosing
Consider potential results (edge: tirzepatide), tolerability (individual), and cost/access (varies, and compounded options change the math). A provider can help you weigh these — and if budget is the deciding factor, read what GLP-1 really costs.
See which option fits your goals and budget
Check your eligibility with a licensed provider — free, online, no insurance required.
Check Your Eligibility