Mounjaro vs Wegovy results: what the trials actually found

Ask Mounjaro vs Wegovy results and you want one thing: the numbers from the actual trials, not a brochure. Here they are, side by side, with the caveats that matter. The short version is that Mounjaro (tirzepatide) produced the larger average weight loss in its headline trial, while Wegovy (semaglutide) is the more established jab and the only one shown to cut heart attack and stroke risk in people with existing heart disease. Neither of those facts settles which is right for you — a prescriber does that — but they frame the whole fight.

What each trial actually measured

The headline results come from two separate studies, so a like-for-like comparison needs a little care. Both enrolled adults with obesity or overweight without type 2 diabetes, both ran for well over a year, and both compared the drug against placebo alongside lifestyle changes. But they were run at different times, on different groups, and at different top doses.

Mounjaro — SURMOUNT-1

SURMOUNT-1 followed adults over 72 weeks. Mean weight loss came out at 16.0% on the 5 mg dose, 21.4% on 10 mg and 22.5% on 15 mg, versus about 2.4% on placebo. Roughly 90% of people on the 15 mg dose lost at least 10% of their body weight — a strikingly high responder rate.

Wegovy — STEP 1

STEP 1 followed adults over 68 weeks at the 2.4 mg maintenance dose. Mean weight loss was −14.9% (about 15%), versus roughly 2.4% on placebo. That result is what turned semaglutide into the reference point every newer drug is now measured against.

Mounjaro vs Wegovy: the results table

Because the trials aren't identical, treat this as a fair summary rather than a stopwatch photo-finish. The doses shown are each drug's studied top dose.

Why the head-to-head trial matters more

Comparing two separate placebo trials is useful but imperfect. The cleaner evidence comes from studies that put both drugs in the same room. In a direct head-to-head, tirzepatide produced more weight loss than semaglutide — roughly 20% versus roughly 14% in the population studied — which lines up with what the separate trials suggested. When two independent lines of evidence point the same way, the finding is harder to argue with.

Where Wegovy pulls ahead

Bigger weight-loss numbers aren't the whole story, and this is where the "results" question stops being about the scales. Wegovy is the most established dedicated weight-loss jab, with the longest real-world track record in the UK. More importantly, it is the only one of these medicines shown in a major trial (SELECT) to cut the risk of heart attack and stroke in people who already have cardiovascular disease. For someone whose main concern is heart risk rather than the last few percentage points on the scale, that evidence can matter more than a larger average loss.

The tablet in the corner

A third result is worth knowing about. The Wegovy Pill — oral semaglutide, the UK's first needle-free GLP-1 — averaged about 13.6% body-weight loss over 64 weeks at the 25 mg dose in the OASIS 4 trial, and about 16.6% among people who took it consistently. Around 30% of participants lost at least 20% of their body weight. It won't out-lose Mounjaro on the averages, but "close to the jab, without the needle" is a genuine result for anyone who dreads injections.

So which result should decide it?

If the single question is how much weight, on average, the trials favour Mounjaro. If the question is proven, established, heart-protective, Wegovy has evidence Mounjaro's headline trials weren't designed to produce. Both are prescription-only medicines, both carry side effects, and the right choice — and the right dose — is always the prescriber's call, made with your medical history in front of them.

For the full picture beyond weight loss, see our complete Mounjaro vs Wegovy comparison, weigh the side effects of each, and check what each actually costs in our price breakdown. Already on Wegovy and tempted by the bigger numbers? Read our guide to switching from Wegovy to Mounjaro first, or start at the live price table on our homepage.

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