Why people ask whether Mounjaro is better than Wegovy — and what the evidence actually says

You've seen the headline: Mounjaro 'beats' Wegovy. Here's what that actually means

Imagine you're weighing up two treatments and a friend sends you an article saying Mounjaro is simply better. The headline comes from real data, but the full picture is more nuanced.

The SURMOUNT-1 trial (published in the New England Journal of Medicine) followed adults with obesity over 72 weeks and found average body-weight reductions of around 20–21% at the 15 mg dose. The STEP 1 trial for semaglutide 2.4 mg reported around 15% over 68 weeks. Both figures are from well-run, large, placebo-controlled trials, but they were separate studies with different participant groups, so you cannot stack them directly.

The SURMOUNT-5 trial changed that. Published in the New England Journal of Medicine in 2025, it ran tirzepatide head-to-head against semaglutide 2.4 mg in 751 adults with obesity and no diabetes over 72 weeks, and if you want a thorough breakdown of what that result means in practice, our page on whether tirzepatide is better than Wegovy works through the evidence in detail. NICE's appraisal of tirzepatide (TA1026) notes the indirect comparisons favour tirzepatide, and the committee had SURMOUNT-5 available before publication of its September 2025 update.

So the headline holds, on average, in a direct comparison. The question is whether "on average" applies to you specifically, and that requires a prescriber's assessment, not a comparison article.

The mechanism gap, and why Wegovy 7.2 mg narrows the numbers

Mounjaro activates two receptors: GIP and GLP-1. Wegovy activates one: GLP-1. The dual action appears to produce stronger signalling around appetite, energy use and gastric emptying, which is the leading explanation for the larger average weight loss.

Wegovy, though, did not stand still. The MHRA approved a higher 7.2 mg maintenance dose in early 2026, and a dedicated single-dose 7.2 mg pen followed in April 2026. Trials for the higher dose reported around 20.7% average weight loss over 72 weeks, closing the gap with tirzepatide's 15 mg results considerably. Anyone comparing these two medicines on results alone needs to factor in which Wegovy dose they'd actually be prescribed, not just the original 2.4 mg figure, and our guide on whether Mounjaro is better than Wegovy runs through the dose-by-dose picture in full. For a detailed look at how that changes the numbers, this comparison of Wegovy and Mounjaro runs through the dose-by-dose picture.

Side-effect profiles are similar: nausea, loose stools, constipation and fatigue are common to both, most noticeable when starting or after a dose increase, and usually settle within a couple of weeks. Neither medicine is tolerated identically by every person. Some people do better on one than the other for reasons a trial average cannot predict. The NHS tirzepatide medicines page and its semaglutide equivalent both carry the full side-effect lists if you want to compare them directly before your consultation.

Side-by-side: what the key facts look like in one place

Numbers above are from published trials; individual results vary. Both medicines are prescription-only and require clinical assessment before any supply.

Eligibility, oral contraceptives, and the things that actually tip the decision

The trial results matter, but prescribers weigh several other factors when recommending one over the other. Eligibility criteria are broadly similar (adults with a BMI of 30 or above, or 27 or above with a qualifying condition such as hypertension, high cholesterol or type 2 diabetes) and lower BMI thresholds apply for some ethnic backgrounds under UK guidance.

One practical difference: women taking oral contraceptives should add a non-oral method of contraception for the first four weeks of Mounjaro and for four weeks after each dose increase, because tirzepatide's effect on gastric emptying may reduce pill absorption. NHS guidance notes no equivalent evidence of reduced pill effectiveness for semaglutide, and if you are weighing up how tirzepatide and semaglutide differ on points like this, our page on whether Mounjaro is better than semaglutide covers the comparison in more detail. That isn't a reason to avoid Mounjaro, but it is a conversation to have before starting. For more detail on drug interactions that affect this decision, this piece on Mounjaro versus Ozempic covers the absorption point in a different context.

Cost is also part of the picture. Eli Lilly raised Mounjaro's UK list price from September 2025, higher doses now carry list prices around £330 per four-week pen, and private market prices vary widely. A full cost comparison is covered on the Mounjaro vs Wegovy price page. The short version: the cheapest option is not necessarily the right question for a prescription medicine; what you're actually weighing is clinical suitability and supply-chain safety.

Which of these medicines suits you is a clinical decision. Our prescribers at nume work through your health history, current medicines and goals in your free consultation, and they make that recommendation with you, not for you. Check your eligibility and start your free consultation if you'd like to take it further.