Is Wegovy as effective as Mounjaro for weight loss?

You've read that Mounjaro 'beats' Wegovy, here's what the data really say

The comparison you've probably seen references the SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025. It was an open-label, head-to-head study in 751 adults with obesity but without type 2 diabetes, running for 72 weeks. Participants received either tirzepatide (up to 15mg) or semaglutide at its standard 2.4mg maintenance dose. Tirzepatide produced meaningfully greater average weight reduction, and if you're wondering whether Mounjaro is genuinely more effective than Wegovy, the trial data give a clearer answer than most headlines do. NICE's appraisal of tirzepatide (TA1026) also noted that indirect comparisons across the wider trial programmes favour tirzepatide.

What the headline misses: SURMOUNT-5 compared tirzepatide against the 2.4mg Wegovy dose that was the ceiling at the time. The MHRA approved a higher 7.2mg semaglutide dose in early 2026, with trial data showing around 20.7% average weight loss over 72 weeks, closer to tirzepatide 15mg territory. So if you've been asking whether Wegovy is less effective than Mounjaro, the gap that made the news is already narrower than it was. The table below reflects the position as the evidence stands now.

Numbers in any trial are averages. Some people respond strongly to semaglutide; others find tirzepatide better tolerated. If you want to look more closely at the evidence behind claims that Wegovy is not as effective as Mounjaro, the table tells you what groups did on average, not what you will do.

How the two medicines differ in practice, beyond the weight-loss figures

Mounjaro works on two gut-hormone pathways (GIP and GLP-1) where Wegovy targets GLP-1 alone. Whether that dual action translates into a meaningful difference for a specific patient is something a prescriber works out over time, watching how you respond and tolerate each dose step. Both start at a low tolerability dose and are titrated gradually over months; neither jumps straight to the maintenance level.

Side-effect profiles are broadly similar: nausea, changes in bowel habit, and fatigue are the most commonly reported with both, typically most noticeable after a dose increase and settling over days to a few weeks. The NHS patient information for tirzepatide and the equivalent page for semaglutide set out the full lists. One practical difference: people using oral contraceptives alongside Mounjaro are advised to add a non-oral method of contraception for the first four weeks of treatment and for four weeks after each dose increase, because tirzepatide can slow gastric emptying in a way that reduces pill absorption. NHS guidance does not flag the same concern for semaglutide.

Storage is the same for both injections: refrigerated at 2–8°C; the exact room-temperature window is in each medicine's Patient Information Leaflet and is the figure to follow. If you're researching the practical differences between Wegovy and Mounjaro in more depth, we've covered those separately.

Which one can you actually access, and through what route?

Both are prescription-only medicines, the only legal route is a prescription following a genuine clinical assessment. Worth saying plainly: anyone offering either medicine without that step is operating outside UK law, and the MHRA has seized large volumes of fake pens from unverified online sellers.

On the NHS, access to both medicines is currently restricted to specific eligibility cohorts and involves waiting lists that can be long. Tirzepatide on the NHS requires a BMI of at least 35 plus qualifying conditions, phased in by cohort; Wegovy is available via specialist weight management services under NICE TA875 criteria. The eligibility detail matters, our treatment overview explains both routes clearly.

Through a regulated private pharmacy like ours, the private licensed eligibility is broader (BMI ≥30, or ≥27 with a weight-related condition), there is no waiting list, and a prescriber can review your consultation the same day. When your treatment is approved, you'll get a DPD tracking notification and the medicine arrives in a plain, unmarked box, nothing on the outside to indicate what's inside. For a detailed breakdown of how costs compare between the two medicines, our page on Mounjaro vs Wegovy pricing in the UK covers that specifically.

Our clinical team reviews every consultation personally. If you're weighing up whether Wegovy is as effective as Mounjaro for weight loss in your specific situation, that conversation is the right place to have it, not a comparison table. Start your free consultation and a prescriber will assess your full picture.