How Good Is Wegovy Compared to Mounjaro? What the Evidence Says

The result that matters: how much weight do people actually lose?

In the SURMOUNT-1 trial, published in the New England Journal of Medicine, adults taking tirzepatide (the medicine in Mounjaro) at the highest dose saw an average body-weight reduction of around 20–21% over 72 weeks, alongside a reduced-calorie diet and increased activity. That figure placed it among the most effective medicines ever studied for weight management. For context, Wegovy's comparable trial (STEP 1, 68 weeks, semaglutide 2.4mg) produced an average of roughly 15%. So at the doses studied in those trials, tirzepatide pulled ahead. When researchers compared them directly in the SURMOUNT-5 trial (reported in the New England Journal of Medicine in 2025) tirzepatide again produced greater average weight loss than semaglutide 2.4mg over 72 weeks, which is currently the strongest head-to-head evidence available, and you can read a full breakdown of that evidence on our page covering how Wegovy compares to Mounjaro. It is worth noting that Novo Nordisk's newer 7.2mg dose of Wegovy, approved by the MHRA in early 2026, produced around 20.7% average weight loss in its own trials, bringing it much closer to Mounjaro's results. NICE reviewed the evidence for tirzepatide and recommended it for eligible adults in technology appraisal TA1026.

Different mechanisms, different profiles, why this affects your decision

The two medicines work through related but distinct pathways. Mounjaro activates both the GLP-1 and GIP receptors, making it the only dual-agonist weight-loss medicine licensed in the UK. Wegovy acts on GLP-1 receptors only. Both slow gastric emptying and reduce appetite, which is why the side-effect profiles look similar: nausea, vomiting, diarrhoea and constipation are the most frequently reported effects with each, generally most noticeable early in treatment or after a dose increase, and typically settling within days to a couple of weeks. You can read more about how the two mechanisms compare in practice on a dedicated page. One practical difference that matters for some people: NHS England guidance notes that women using oral contraceptives should add a non-oral method for the first four weeks of Mounjaro treatment and for four weeks after each dose increase, because absorption of the pill may be reduced; the same caution does not currently apply with semaglutide. Similarly, the guidance advises considering transdermal HRT while taking tirzepatide. These are not reasons to rule Mounjaro out, but they are worth discussing with a prescriber before you start. Our clinical team reviews precisely these details during consultation.

Comparing key facts side by side

The table below summarises the verified, factual differences between the two medicines. Numbers from SURMOUNT-1, STEP 1, and NICE appraisals; consult the NHS tirzepatide page and the equivalent NHS semaglutide page for full patient-level detail on side effects and storage.

So which one should you choose?

This is where the clinical decision replaces the comparison table. Trial averages describe populations; they do not predict what will happen for you. Your medical history, any medicines you already take, your BMI, any weight-related conditions, your preference for an injection versus a tablet, all of it matters. The broader Wegovy versus Mounjaro picture also touches on cost differences, which are real; you can read about why the two medicines are priced differently if that is part of your thinking. And if you have come to this page partly because you have heard about Ozempic and wondered where it fits: Ozempic is semaglutide licensed for type 2 diabetes, not weight management, and is not prescribed for that purpose through nume's service. The right starting point is a conversation, not a ranking. Our prescribers work through these factors with you at no charge; eligibility is confirmed during that consultation, not assumed before it. Speak to our prescribers and let the clinical picture, rather than a table, guide the decision.