Ozempic vs Wegovy vs Mounjaro vs Zepbound: what's actually different?

Same two drugs, four brand names

Ozempic, Wegovy, Mounjaro and Zepbound get talked about like four separate products racing each other on TikTok and in doctors' offices. They're actually two drugs. Ozempic and Wegovy both contain semaglutide, made by Novo Nordisk. Mounjaro and Zepbound both contain tirzepatide, made by Eli Lilly. In each pair, one brand is approved for type 2 diabetes and the other for chronic weight management, same molecule, different label and often a different maximum dose. Most comparison articles stop at that molecule-and-indication split and leave it vague which one actually works better. A real head-to-head trial answered that question in 2025, and the answer comes with caveats worth knowing before you repeat the headline number.

The trial that actually compared them

SURMOUNT-5, published in the New England Journal of Medicine in May 2025, randomly assigned 751 adults with obesity but without diabetes to either tirzepatide or semaglutide, each at the maximum tolerated dose, for 72 weeks. Tirzepatide produced an average 20.2% drop in body weight. Semaglutide produced 13.7%. Thirty two percent of the tirzepatide group lost at least a quarter of their starting weight, compared with 16% on semaglutide. That's a real, statistically significant gap, not marketing spin, and it lines up with the drugs' mechanisms: tirzepatide works on two gut hormone receptors, GLP-1 and GIP, while semaglutide works on GLP-1 alone. Louis Aronne, MD, director of the Comprehensive Weight Control Center at Weill Cornell Medicine and a lead investigator on the trial, summed up why a trial like this mattered: "Doctors, insurance companies and patients are always asking, 'which drug is more effective?'"

The caveat nobody's SEO listicle mentions

Here's the gap in most coverage of this trial: SURMOUNT-5 was open-label, meaning participants knew which drug they were on, and it was funded by Eli Lilly, tirzepatide's maker. Neither detail erases the result, but both are worth knowing before treating 20.2% versus 13.7% as gospel. The trial also compared maximum tolerated doses available at the time it was designed, and semaglutide dosing has continued to evolve since. None of that means tirzepatide's edge is fake. It means the real-world gap between a well-dosed course of either drug is probably smaller than the trial's topline numbers suggest, and individual response varies more than any average.

What actually differs beyond the molecule

Beyond raw weight loss, a few practical differences matter more day to day. Ozempic has FDA-approved uses semaglutide's weight-loss sibling doesn't, including reducing cardiovascular risk in people with type 2 diabetes and heart disease, and a kidney-protection indication. Tirzepatide's drugs don't carry those approvals yet. Side effects run similar across both, mostly nausea, vomiting and digestive upset that tends to ease after the first few weeks, though reported discontinuation rates in SURMOUNT-5 were somewhat lower on tirzepatide (2.7%) than semaglutide (5.6%) specifically for gastrointestinal reasons. Dosing schedules differ slightly between the brands too, which is one more reason switching between any of these four names should go through a doctor rather than guesswork, as we've covered with other GLP-1 trends.

Cost and coverage, the part that decides it for most people

For most people the deciding factor isn't the 6 percentage point gap in a trial, it's what insurance actually covers. Coverage is typically tied to the approved indication rather than the drug itself: a plan might cover Ozempic for diagnosed diabetes while refusing Wegovy, the identical molecule, for weight loss alone, or vice versa for the tirzepatide pair. That makes the real-world choice between these four names less about head-to-head percentages and more about which indication your diagnosis and your insurer's rules actually line up with, alongside interest in other approaches people try alongside GLP-1s.

Our take

Ozempic and Wegovy are one drug; Mounjaro and Zepbound are another. The 2025 head-to-head trial gives tirzepatide a real, measurable edge in average weight loss, but it's an open-label, manufacturer-funded result using a dosing comparison that's already somewhat dated. Neither drug is a magic bullet and neither is interchangeable with the other without medical supervision. The honest comparison is less "which one wins" and more "which one your body tolerates and your coverage actually pays for."

This is general information, not medical advice. Talk to a clinician before changing anything, especially if you are pregnant, nursing, or managing a condition.