Wegovy or Mounjaro: comparing the two licensed weight-loss injections

You've read the same question dozens of ways, here's the honest answer

Most people land on this comparison after a few hours of reading forums, Reddit threads and news articles that all seem to contradict each other. So here is the plain version. Mounjaro activates two gut-hormone receptors, GIP and GLP-1, which is why it is described as a dual agonist. Wegovy activates only the GLP-1 receptor. Both slow gastric emptying and reduce appetite; the dual mechanism in Mounjaro appears to produce greater average weight loss in head-to-head evidence. In the SURMOUNT-5 trial published in the New England Journal of Medicine in 2025, tirzepatide produced meaningfully greater average weight reduction than semaglutide 2.4mg over 72 weeks in adults with obesity and no diabetes. That is the closest to a direct comparison the clinical literature currently offers, and it favours Mounjaro, but averages hide a lot of individual variation.

Wegovy is a once-weekly subcutaneous injection titrated from 0.25mg up to a standard maintenance dose of 2.4mg. A 7.2mg dose was approved by the MHRA in January 2026 and a dedicated single-dose pen for it followed in April 2026, narrowing the average weight-loss gap with tirzepatide's top dose. The NHS medicines page for semaglutide covers the established dose pathway in detail. Mounjaro runs from 2.5mg up to 15mg across six strengths, with the starter dose designed to let your system adjust before the prescriber considers stepping up. Our detailed Wegovy vs Mounjaro breakdown goes further on mechanism if you want the science.

The numbers side by side, what trials actually showed

The table below draws on data from NICE's appraisal of tirzepatide (TA1026) and the published STEP 1 and SURMOUNT-1 trial results. Treat these as population averages in controlled research settings, individual results vary.

The GI side-effect profiles overlap significantly. Both are Black Triangle (▼) medicines under additional MHRA monitoring. For a closer look at how cost factors in when choosing, our Mounjaro vs Wegovy price comparison runs through the UK private market context.

Who each medicine is licensed for, and how eligibility works in practice

The licensed eligibility criteria are broadly the same: adults with a BMI of 30 or above, or 27 or above alongside a qualifying condition such as high blood pressure, type 2 diabetes, high cholesterol or obstructive sleep apnoea. For people from South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds, UK guidance applies thresholds 2.5 kg/m² lower. Neither medicine is licensed for use during pregnancy, breastfeeding or when trying to conceive, and neither is licensed for under-18s.

On the NHS, access to both medicines is phased and restricted, Mounjaro under NICE TA1026 requires a BMI of at least 35 plus qualifying comorbidities, while Wegovy under NICE TA875 is restricted to specialist weight management services for a maximum of two years. Private prescribing follows the licensed SmPC criteria, which are somewhat broader. A prescriber at a regulated pharmacy reviews your full picture (not just your BMI figure) before deciding whether treatment is clinically appropriate. If you want to understand our clinical team's approach to that review, our clinical lead's profile sets out the oversight model.

One practical point: women taking the oral contraceptive pill should add a non-oral method of contraception for the first four weeks of Mounjaro and for four weeks after each dose increase, because absorption of the pill may be reduced. The NHS England guidance on weight-management injections covers this in full. There is no equivalent recommendation for semaglutide at present. It is worth raising with your prescriber before you start either medicine.

Switching, combining and what 'better' actually means

People sometimes ask whether they can take both, switch between them, or move from one to the other if results plateau. Combining them is not supported by evidence or licensing. Switching is possible under clinical supervision, many patients who move from Wegovy to Mounjaro do so when a prescriber judges it appropriate, and real-world switching accounts reflect that experience varies. Our guide to which performs better and the broader what's better, Mounjaro or Wegovy page explore that question from different angles if you want more detail before your consultation.

The honest answer to "which is best" is that it depends on factors your prescriber is better placed to weigh than any article: your existing conditions, your medication history, how your body has responded to any previous treatment, and your preferences around dose progression and side-effect tolerance. If you are still weighing up the two options, our dedicated page on which is better, Mounjaro or Wegovy, pulls together the evidence in one place to help you prepare for that conversation. The SURMOUNT-5 evidence does favour tirzepatide on average weight loss in a head-to-head trial. But a larger average across a trial population tells you something useful without telling you exactly what will happen for you. Which suits you is a clinical decision our prescribers make with you. Start your free consultation and a GPhC-registered prescriber will review your answers the same day.