Same drug, different label? Not quite. How the four best-known GLP-1 medications actually differ — in how they work, how much weight you can expect to lose, and what they cost.
Ozempic and Wegovy are the same drug (semaglutide) with different FDA labels — Ozempic for type 2 diabetes, Wegovy for weight loss. Mounjaro and Zepbound are the same drug (tirzepatide), split the same way — Mounjaro for diabetes, Zepbound for weight loss. Head-to-head, tirzepatide produces greater weight loss than semaglutide on average, but both are highly effective. All four are once-weekly injections with similar side effect profiles.
All four belong to a class of medications called incretin mimetics. Semaglutide (Ozempic, Wegovy) mimics a single gut hormone called GLP-1 (glucagon-like peptide-1). Tirzepatide (Mounjaro, Zepbound) mimics two: GLP-1 plus a second hormone called GIP (glucose-dependent insulinotropic polypeptide). This dual action is why tirzepatide tends to outperform semaglutide on weight loss in clinical trials.
All four drugs do essentially the same things inside the body: they prompt the pancreas to release insulin when blood sugar rises, they slow stomach emptying so food stays with you longer, and they signal the brain to reduce appetite. The result is better blood sugar control and, for most people, significant weight loss.
| Drug | Active ingredient | FDA-approved for | Made by | Dosing |
|---|---|---|---|---|
| Ozempic | Semaglutide | Type 2 diabetes; cardiovascular risk reduction | Novo Nordisk | Weekly injection, 0.25-2.0 mg |
| Wegovy | Semaglutide | Chronic weight management; cardiovascular risk reduction; MASH (fatty liver) | Novo Nordisk | Weekly injection, 0.25-2.4 mg |
| Mounjaro | Tirzepatide | Type 2 diabetes | Eli Lilly | Weekly injection, 2.5-15 mg |
| Zepbound | Tirzepatide | Chronic weight management; obstructive sleep apnea in adults with obesity | Eli Lilly | Weekly injection, 2.5-15 mg |
This is the question most people actually want answered. The numbers below come from large randomized clinical trials, where participants took the medication in combination with diet and lifestyle counseling over roughly 68-72 weeks.
| Drug | Average weight loss | Key trial |
|---|---|---|
| Wegovy (semaglutide 2.4 mg) | ~15% of starting body weight at 68 weeks | STEP 1 |
| Zepbound (tirzepatide 15 mg) | ~21% of starting body weight at 72 weeks | SURMOUNT-1 |
| Ozempic (off-label for weight) | Typically 5-10% (lower doses) | SUSTAIN trials |
| Mounjaro (off-label for weight) | Similar to Zepbound at same dose | SURPASS trials |
Until 2025, there was no direct comparison of tirzepatide against semaglutide for weight loss. SURMOUNT-5, published in the New England Journal of Medicine in May 2025, changed that. Over 72 weeks, participants with obesity but without diabetes lost an average of 20.2% of body weight on tirzepatide versus 13.7% on semaglutide — a difference of roughly 6.5 percentage points, which translates to about 20 additional pounds for a 200-pound starting weight.
Tirzepatide also produced greater reductions in waist circumference (18.4 cm vs. 13.0 cm). Both drugs improved blood pressure, A1C, fasting glucose and lipid levels. Adverse events were comparable, though discontinuations due to gastrointestinal side effects were slightly higher with semaglutide (5.6%) than tirzepatide (2.7%).
For readers coming from our A1C Drugs page, here's how these drugs affect hemoglobin A1C in patients with type 2 diabetes:
To put that in perspective: many older diabetes drugs (Januvia, Byetta, Farxiga) reduce A1C by roughly 0.8 to 1.0 percentage points. The GLP-1 and GIP/GLP-1 medications are in a different league for glycemic control, which is why they have largely displaced older drugs in first-line treatment guidelines.
All four drugs share the same side effect profile because they work on the same pathways. The most common issues are gastrointestinal, especially during the first several weeks and after each dose increase:
Most GI side effects are mild to moderate and improve over time. Slow dose escalation — starting low and increasing gradually over months — is the standard strategy for minimizing them.
All four drugs carry an FDA "boxed warning" for a rare type of thyroid tumor (medullary thyroid carcinoma) based on rodent studies. They should not be used by anyone with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
Other rare but serious risks include pancreatitis, gallbladder problems, kidney injury related to dehydration from GI side effects, and severe allergic reactions.
Brand-name pricing without insurance in the U.S. is roughly:
Insurance coverage varies widely. Diabetes indications (Ozempic, Mounjaro) are more commonly covered than weight-loss indications (Wegovy, Zepbound), though Medicare rules have been evolving for weight-loss prescriptions tied to cardiovascular risk.
Compounded semaglutide and tirzepatide — produced by compounding pharmacies during the 2023-2024 shortages — were much cheaper but are increasingly restricted now that the FDA has declared both drugs off shortage. If you see offers well below brand-name pricing, check the legal and safety status before proceeding.
The right drug depends on your primary goal, your insurance, and how your body responds. A few rules of thumb:
If you have type 2 diabetes and your main concern is blood sugar control, Ozempic and Mounjaro are the drugs labeled for you. Mounjaro tends to lower A1C slightly more, and also produces more weight loss as a bonus. Insurance is more likely to cover these than the weight-loss branded versions.
If you don't have diabetes and your goal is weight loss, Wegovy and Zepbound are the FDA-approved options. Zepbound produces more weight loss on average in head-to-head data, but individual response varies and Wegovy has a longer track record including strong cardiovascular outcomes data.
If cost is the deciding factor, check both manufacturer savings cards (Novo Nordisk for Ozempic/Wegovy, Eli Lilly for Mounjaro/Zepbound) and your plan's formulary. Lilly's direct-to-consumer Zepbound vials have been the most aggressive cash-pay pricing from a major manufacturer.
If you've tried one and plateaued, switching from semaglutide to tirzepatide is increasingly common and has clinical support. Talk to your prescriber about titration.
Yes, both contain semaglutide. The difference is the maximum dose (2.0 mg for Ozempic, 2.4 mg for Wegovy) and the FDA-approved indication. Pharmacologically, they're the same molecule.
Yes, both contain tirzepatide. Same molecule, same dose range (2.5-15 mg), different labels. Eli Lilly split them into two brands so each could be approved, marketed, and potentially reimbursed separately.
On average, yes, for weight loss. The SURMOUNT-5 head-to-head trial showed roughly 20% vs. 14% body weight reduction over 72 weeks. But averages conceal individual variation — some people lose more on semaglutide than they would on tirzepatide, and tolerability may differ.
Any rapid weight loss — from these drugs, from dieting, or from bariatric surgery — includes some lean mass loss alongside fat loss. Protein intake (roughly 1.2-1.6 g per kg of body weight) and resistance training meaningfully reduce that loss. This is an active area of research.
Appetite regulation returns to baseline, and most people regain a substantial portion of the lost weight over 12 months unless they have established durable lifestyle and dietary changes. These drugs are generally considered long-term therapies, similar to blood pressure or cholesterol medications, rather than short courses.
Wegovy and Zepbound are approved for adults with obesity (BMI ≥30) or overweight (BMI ≥27) with at least one weight-related health condition such as high blood pressure, high cholesterol, type 2 diabetes, or sleep apnea. They are not approved for purely cosmetic weight loss.