Wegovy vs Mounjaro: comparing two licensed weight-loss injections

You've seen the results headlines, here's what the trials actually showed

Picture the moment most people arrive at this comparison: you've come across a claim that one injection causes dramatically more weight loss than the other, and you want to know if it's true. The short answer is yes, on average, but with real nuance attached.

Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two separate gut-hormone pathways involved in appetite regulation and blood-sugar control. Wegovy works on one of those pathways, the GLP-1 receptor, which it shares with Ozempic, though Wegovy and Ozempic are not the same product, and only Wegovy is licensed for weight management. The mechanistic difference matters clinically, and it shows up in the data.

In SURMOUNT-1, published in the New England Journal of Medicine, tirzepatide at its highest dose produced average body-weight reductions of around 20–21% over 72 weeks in adults with obesity. In the STEP 1 trial, semaglutide 2.4mg averaged roughly 15% over 68 weeks. The SURMOUNT-5 head-to-head trial, published in the NEJM in 2025, confirmed that tirzepatide produced greater average weight loss than semaglutide 2.4mg in a direct comparison, and if you want a thorough breakdown of what that means in practice, our page on Monjaro vs Wegovy walks through the evidence in full. NICE's appraisal of tirzepatide (TA1026) also notes that indirect comparisons favour tirzepatide. The important caveat: Wegovy's 7.2mg maintenance dose, approved by the MHRA in January 2026, reported average weight loss of around 20.7% over 72 weeks, bringing it much closer to Mounjaro's figures than the older 2.4mg data would suggest.

Eligibility: the thresholds that decide which prescription you can receive

Both medicines share a similar licensed BMI floor) 30, or 27 with at least one weight-related condition such as high blood pressure, high cholesterol, type 2 diabetes, obstructive sleep apnoea or osteoarthritis. That said, NICE's recommendations sit on top of the licence, and they differ between the two products.

NICE recommends Mounjaro (TA1026) for adults with a BMI of 35 or above alongside at least one weight-related comorbidity, with lower BMI thresholds for South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean backgrounds. Wegovy is recommended under TA875 for a similar population but only when treatment is delivered within a specialist weight management service and for a maximum of two years, criteria that reflect how the NHS structures access rather than the medicine's own licence. For private patients, the licensed eligibility criteria apply, and your prescriber weighs up your full health picture regardless of which product is being considered. You can read more about how Wegovy fits into the private-prescription landscape on its own page.

Lower BMI thresholds can apply for some ethnic backgrounds under UK guidance, worth raising at consultation if relevant to you. BMI alone is never the whole story; the prescriber reviews contraindications, current medicines and your overall health before recommending either product. Under-18s, people who are pregnant, breastfeeding or actively trying to conceive should not use either medicine.

Side effects and practical differences worth knowing before you decide

The side-effect profiles of both medicines are led by gastrointestinal symptoms: nausea, constipation, diarrhoea, reflux and fatigue appear in trials for both, most noticeably in the early weeks or after a dose increase, and tend to ease as the body adjusts. Neither is side-effect-free, and honest prescribing acknowledges that. The MHRA issued a Drug Safety Update in January 2026 highlighting acute pancreatitis as an infrequent but serious risk across GLP-1 medicines; severe, persistent stomach pain that spreads to the back warrants urgent medical attention regardless of which treatment you're on. Side effects suspected with either medicine can be reported at yellowcard.mhra.gov.uk.

On practicalities: Mounjaro uses a KwikPen that delivers four weekly doses per pen; Wegovy comes in individual pre-filled pens per injection. Both are injected once a week into the abdomen, thigh or upper arm, rotated each time, and both need to be kept in the fridge. One thing worth knowing if you're on the combined oral contraceptive pill and considering Mounjaro: the MHRA advises adding a non-oral method of contraception for the first four weeks of treatment and for four weeks after each dose increase, because gut-slowing can reduce pill absorption. That same caution applies less clearly to semaglutide, though your prescriber will go through this with you. If you'd like a closer look at how the two compare on specific questions, the key differences between Mounjaro and Wegovy are explored in more detail on a dedicated page.

How to move from comparison to prescription

Reading a comparison page is a reasonable starting point. Stopping there isn't. The question of which medicine suits you (given your BMI, your comorbidities, your other medicines, your preferences around injection devices and your history with GI symptoms) is one a prescriber answers, not a search engine.

At nume, the process is straightforward. Complete a free online consultation, and a named GPhC-registered Independent Prescriber reads your answers the same day. There's no algorithm making that call, a real clinician reviews it. If you order before 12pm on a weekday and your consultation is approved, your treatment is dispatched the same day and delivered free the next working day by DPD. Everything is in one transparent price: consultation, prescription, treatment and aftercare. No subscription, no auto-renewal. If you want to understand how the clinical evidence positions one over the other in more depth before you start, our page covering what's better, Monjaro or Wegovy, goes into the trial data and practical considerations in detail. Alternatively, start your free consultation and let one of our prescribers work through it with you directly.