What's the difference between Mounjaro and Wegovy?

Do Mounjaro and Wegovy work the same way?

No, and the difference matters clinically. Wegovy contains semaglutide, a GLP-1 receptor agonist: it mimics a gut hormone that signals fullness, slows gastric emptying and reduces appetite. Mounjaro contains tirzepatide, described as a dual GIP and GLP-1 receptor agonist — it activates both the GLP-1 pathway and the GIP (glucose-dependent insulinotropic polypeptide) pathway. GIP receptors are found in fat tissue, the brain and the gut, so adding that second signal appears to amplify the appetite-suppressing and metabolic effects beyond what GLP-1 alone achieves. That dual mechanism is why tirzepatide is sometimes described as the first of its kind; semaglutide works through a single, well-established pathway that is nonetheless highly effective. The NHS tirzepatide medicine page and the NHS semaglutide page both give plain-English summaries of how each works, including their side-effect profiles. Neither medicine is a fat-burner in any direct sense; both reduce the drive to eat, and weight change follows from that.

It is also worth being precise about brand names: Mounjaro is tirzepatide for weight management; Ozempic is also semaglutide but is licensed only for type 2 diabetes, not for weight loss. If someone quotes you an Ozempic prescription for weight management, that is off-label use, which is a separate conversation to have with a prescriber.

What does the evidence say about weight-loss results?

Clinical trial results favour tirzepatide, though both medicines have strong data. In SURMOUNT-1, adults without diabetes lost an average of around 20–21% of body weight over 72 weeks at the 15mg dose of tirzepatide, based on findings published in the New England Journal of Medicine. The STEP 1 trial for semaglutide 2.4mg reported around 15% average weight reduction over 68 weeks. SURMOUNT-5, a head-to-head randomised trial published in the New England Journal of Medicine in 2025, directly compared the two in adults with obesity and no diabetes: tirzepatide produced a statistically greater average weight reduction than semaglutide 2.4mg over 72 weeks. NICE cited indirect comparisons favouring tirzepatide in its appraisal of both medicines.

There is an important footnote. Wegovy now has a higher licensed dose in the UK: the MHRA approved a 7.2mg maintenance dose, with a dedicated single-dose pen approved on 14 April 2026. Early data for 7.2mg showed around 20.7% average weight loss over 72 weeks, which narrows the gap with tirzepatide 15mg considerably. Trial averages are population results; individual responses vary, and neither medicine works the same way in every person.

Who qualifies for each, and are the criteria the same?

The licensed eligibility for private prescribing is broadly similar: adults with a BMI of 30 or above, or 27 or above alongside at least one weight-related condition such as high blood pressure, type 2 diabetes, high cholesterol or obstructive sleep apnoea. For some ethnic backgrounds, UK guidance applies thresholds 2.5 kg/m² lower. You can explore the full picture of qualifying conditions for Wegovy and the equivalent criteria for Mounjaro on their respective pages.

On the NHS the two medicines diverge. NICE's appraisal of tirzepatide (TA1026) recommends it for adults with a BMI of 35 or above plus at least one weight-related comorbidity, with NHS rollout phased by how many conditions a person has. Wegovy's NHS recommendation under TA875 specifies use within a specialist weight management service for a maximum of two years. Waiting lists for both NHS routes are long in many areas. Private treatment through a regulated pharmacy is an alternative for people who meet the clinical criteria but cannot access the NHS pathway quickly.

A note on spelling: searches for Monjaro vs Wegovy and Munjaro vs Wegovy all refer to the same comparison, the medicine is Mounjaro, made by Eli Lilly.

Which one should you choose?

That question belongs in a clinical consultation, not on a product page. The right medicine depends on your health history, any conditions you have, medicines you already take, and factors your prescriber weighs that no comparison table can capture. For example, tirzepatide's dual mechanism means specific guidance applies to oral contraceptives during the first weeks of treatment and after dose increases, because gastric emptying slows enough to affect pill absorption, something a prescriber will flag and a GP or sexual health clinic can advise on. For semaglutide, NHS guidance notes no equivalent evidence of reduced oral contraceptive effectiveness.

What arrives in the post is the same in both cases: a plain, unbranded box, tracked by DPD, carrying a pre-filled injection pen. The clinical decision about which pen is right for you is made before it ships. At nume, a GPhC-registered Independent Prescriber reviews your consultation personally, you can read more about our clinical team and what that process involves. If you would find it useful to understand how Manjaro and Wegovy differ from each other before deciding, that guidance is available on its own page. If you are also weighing up how Saxenda and Wegovy compare as injectable weight-loss treatments, we cover that in a separate guide. Which medicine suits you is a clinical decision our prescribers make with you.