Mounjaro vs Wegovy: a clear-eyed comparison for UK adults

You've read both names online and now you're not sure which to ask about

It's a question our prescribers hear most weeks. Someone has done their research, seen that Mounjaro and Wegovy are both licensed in the UK for weight management, and arrived at a consultation genuinely unsure which to raise first. That's a sensible place to land. The two medicines share a family resemblance (both are once-weekly injections, both slow gastric emptying and reduce appetite) but the underlying pharmacology is different enough to matter clinically.

Wegovy contains semaglutide, a GLP-1 receptor agonist made by Novo Nordisk. It activates one gut-hormone pathway involved in hunger and blood-sugar regulation. Mounjaro contains tirzepatide, made by Eli Lilly, and it is the only weight-loss medicine in the UK to activate two pathways simultaneously, both GIP and GLP-1 receptors. Whether that dual action translates into a meaningful difference for any individual person is a clinical question; for the average trial participant, it does. You can read more about the pharmacological distinction on our tirzepatide vs semaglutide weight loss comparison page, which goes deeper into the receptor-level science.

Worth checking before you read any comparison figure: look at which dose was studied and over how many weeks. A result from week 68 at 15mg tirzepatide is a different data point from week 32 at 1mg semaglutide. That one habit saves a lot of confusion when reading about either medicine.

What the head-to-head trial found, and what the numbers actually mean

For most of the time these medicines have been on the UK market, comparing them meant looking across two separate trials run against placebo. That changed with the publication of SURMOUNT-5, a 72-week open-label head-to-head trial in 751 adults with obesity but without type 2 diabetes, published in the New England Journal of Medicine in 2025. Tirzepatide produced greater average weight reduction than semaglutide 2.4mg over that period. NICE's appraisal committee for tirzepatide (TA1026) noted that indirect comparisons across the programmes also favoured tirzepatide. If you want a thorough breakdown of those findings, our page on how good Wegovy is compared to Mounjaro walks through what the evidence actually shows.

The comparison table below draws only on figures that are directly cited in trial publications or UK regulatory assessments. No rounding has been applied to the original data.

The 7.2mg Wegovy pen, approved by the MHRA on 14 April 2026, narrows the average outcome gap that the earlier 2.4mg data showed) a detail that often gets missed in older comparisons. Always check the date on the source you're reading.

Eligibility, side effects and the oral alternative, where the two medicines differ day-to-day

Both medicines are licensed for adults with a BMI of 30 or above, or 27 or above alongside at least one weight-related condition such as high blood pressure, high cholesterol or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under NICE's published guidance. Private eligibility is assessed against the licensed criteria; NHS eligibility follows stricter phased thresholds under TA1026 and TA875 respectively.

The side-effect profiles are broadly similar: nausea, changes in bowel habit, indigestion, reduced appetite and occasional fatigue are the most commonly reported effects with both, particularly when the dose is increased. For most people these settle within a couple of weeks at any given level. One practical difference worth knowing: for tirzepatide specifically, women on the combined oral contraceptive pill should use an additional non-oral method of contraception for the first four weeks of treatment and for four weeks after each dose increase, because absorption of the pill may be reduced. The NHS does not flag the same requirement for semaglutide. If this is relevant to you, raise it during your consultation, our clinical team reviews it as a routine part of the assessment.

A newer consideration: Wegovy is now also available as a once-daily tablet (25mg maintenance dose), approved in June 2026 as the first oral GLP-1 licensed for weight management in the UK. For anyone who strongly prefers not to inject, that changes the comparison. You can explore the practical differences in how each medicine works in more detail if that's the angle you're most interested in.

Which one is right for you? That's precisely what the consultation is for

A Mounjaro vs Wegovy comparison can tell you a great deal about averages. It cannot tell you which medicine suits your specific health history, your current medications, your contraceptive method, or your starting weight. That's not a gap in the evidence, it's simply how prescribing works. Our page comparing Wegovy and Mounjaro sets out the key similarities and differences if you want to read further before your consultation. The cost difference between the two is another factor some patients want to factor in, and our prescribers are straightforward about that too.

At nume, the consultation is free and reviewed the same day. If you're transferring from one medicine to the other, or considering your first prescription, the clinical review covers both options and your prescriber explains their reasoning. There's no auto-renewal, every repeat is re-reviewed. Before your consultation, our Wegovy vs Mounjaro guide is a useful reference for the questions worth raising with your prescriber. If you have lingering questions before starting, the FAQs cover many common ones, or you can get in touch with the team directly. When you're ready to move forward, start your free consultation and a prescriber will take it from there.