Mounjaro or Wegovy: which is better for weight loss?

Imagine you've read that Mounjaro produces bigger weight loss, is that the whole picture?

You're sitting with two browser tabs open: one showing Mounjaro results, one showing Wegovy results. The numbers look different, and you want to know whether one is genuinely better or whether you're comparing apples with oranges. The honest answer is: it's a bit of both.

Mounjaro (tirzepatide, made by Eli Lilly) is a dual GIP and GLP-1 receptor agonist, it activates two gut-hormone pathways linked to appetite and blood-sugar regulation, making it the only medicine of its kind licensed for weight management in the UK. Wegovy (semaglutide, made by Novo Nordisk) targets the GLP-1 pathway alone. In their respective pivotal trials, Mounjaro produced average body-weight reductions of around 20–21% at the highest dose over 72 weeks, while Wegovy at 2.4mg produced around 15% over 68 weeks, according to the SURMOUNT-1 and STEP 1 papers published in the New England Journal of Medicine. Those are different trial designs, different populations, so the comparison is imperfect.

The more telling data point is SURMOUNT-5, a direct head-to-head trial published in 2025, in which tirzepatide produced greater average weight reduction than semaglutide 2.4mg in adults with obesity and no diabetes over 72 weeks. NICE's appraisal of tirzepatide (TA1026) also notes that indirect comparisons favour tirzepatide. So on average weight loss at comparable durations, Mounjaro currently holds the edge in the published evidence.

But averages mask individual variation. If you are still weighing up what's best, Mounjaro or Wegovy, for your particular situation, it helps to know that some people lose significantly more on Wegovy and some find Mounjaro's side-effect profile harder to tolerate. The gap also narrows with Wegovy's newer 7.2mg dose, which produced around 20.7% average loss in trials. Your prescriber's job is to weigh all of this against your specific picture.

Side effects, tolerability and what changes when you switch medicines

Both medicines share a broadly similar side-effect profile because both slow gastric emptying and reduce appetite. Nausea, loose stools, constipation, reflux, fatigue and headache are the most commonly reported effects with each, as described on the NHS tirzepatide medicines page. These tend to be most noticeable after starting or after a dose increase and usually settle within a couple of weeks as the body adjusts.

Where the medicines differ is in their effect on oral medicines taken at the same time. For Mounjaro specifically, NHS guidance advises that women taking oral contraceptives add a non-oral method for the first four weeks of treatment and for four weeks after each dose increase, because absorption of the pill may be reduced. There is no equivalent published recommendation for Wegovy at standard doses. This matters in practice: if you rely on an oral contraceptive, it's a real-world difference worth raising at consultation.

Neither medicine is recommended during pregnancy, breastfeeding or when actively trying to conceive, and neither is licensed for use under 18. A history of medullary thyroid carcinoma, multiple endocrine neoplasia type 2, or pancreatitis requires a careful prescriber conversation before starting either. If you develop severe abdominal pain that spreads to your back (with or without vomiting) seek urgent medical help; the MHRA highlighted acute pancreatitis as a known but infrequent risk for GLP-1 medicines in a Drug Safety Update issued in January 2026.

Cost, NHS access and what a private prescription actually covers

NHS access to these medicines is phased and criteria-based. NICE recommends Mounjaro (TA1026) for adults with a BMI of 35 or above plus at least one weight-related condition such as high blood pressure, type 2 diabetes or obstructive sleep apnoea, with lower BMI thresholds for some ethnic backgrounds. The NHS rollout is expanding in cohorts through 2026 and 2027. Wegovy is recommended by NICE under TA875 for use within specialist weight management services for up to two years. Waiting times for both routes vary significantly by area.

Private treatment sidesteps the waiting list but comes at a cost. Eli Lilly raised Mounjaro's UK list price in September 2025, with the highest dose now reported at around £330 per four-week pen; private provider prices across the market typically range from roughly £149 to £375 per month depending on dose and provider. You can explore how those costs compare in more detail on our Mounjaro and Wegovy price comparison page.

At nume, one price covers your consultation, prescription, delivery and aftercare, no subscription, no repeat-fee surprises. Orders placed before 12pm arrive the next working day via DPD, which is useful when a new pen is due mid-week and you don't want a gap in your routine. Our treatment page shows current pricing, and you can read more about how we work on the about us page. You can also verify us directly on the GPhC register at registration number 9012878.

So which one is right for you?

If the evidence alone guided the decision, the majority of people in trials lost more weight on Mounjaro at comparable doses and durations, and SURMOUNT-5 confirmed that in a direct comparison. But clinical suitability is not just about the average result in a trial population. Your prescriber will look at your BMI, your existing conditions, any medicines you take, your preferences around injections or tablets, and whether supply of a specific dose is confirmed. Patients who are still asking whether Wegovy or Mounjaro is better for them will find that some people are better suited to Wegovy, while others find the dual-pathway approach of Mounjaro a better fit.

We have more detail on the specific question of whether you lose more weight on Mounjaro or Wegovy, and a fuller side-by-side look, including guidance on what's better, Wegovy or Mounjaro, across a range of individual factors, on our Wegovy vs Mounjaro page. Our clinical team (led by our GPhC-registered prescribers) reviews every consultation personally. Which medicine suits you is a clinical decision they make with you, not one a comparison table can settle.