Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow 15mg tirzepatide and semaglutide's highest doses compare in practice
You're at 15mg Mounjaro, here's what that dose represents
Reaching 15mg means you've worked through Mounjaro's full titration sequence: 2.5mg, 5mg, 7.5mg, 10mg and 12.5mg before arriving here. That graduated climb exists so your system adjusts gradually; 15mg is the ceiling, not the starting point. At this dose, tirzepatide is activating both the GIP and GLP-1 receptors simultaneously, a mechanism no other UK-licensed weight-loss medicine shares.
In the SURMOUNT-1 trial, participants on 15mg tirzepatide achieved an average body-weight reduction of around 20–21% over 72 weeks, with some analyses reaching approximately 22.5%, figures cited in the SURMOUNT-1 paper published in the New England Journal of Medicine and reviewed in NICE's technology appraisal TA1026. Those figures were measured in adults with obesity and without type 2 diabetes. If you want to understand what the equivalent dose range looks like on the other side, our dose equivalence overview sets out the broader picture, and if you're curious specifically about where the 5mg step sits, our page on what 5mg Mounjaro equates to in Wegovy terms gives useful context on how the two medicines line up earlier in the titration.
The key clinical point: 15mg is licensed in the UK for weight management alongside a reduced-calorie diet and increased physical activity, in adults with a BMI of 30 or above, or 27 or above with at least one weight-related condition. Lower BMI thresholds apply for certain ethnic backgrounds under UK guidance. A prescriber determines whether continuing at this dose is appropriate, usually reviewing whether meaningful weight loss has occurred by six months.
What's Wegovy's equivalent ceiling, and how does it compare?
Wegovy's standard maintenance dose is 2.4mg once weekly. On 14 April 2026 the MHRA approved a higher 7.2mg dose for adults with a BMI of 30 or above, delivered via a dedicated single-dose pen. Trials of 7.2mg semaglutide reported around 20.7% average weight loss over 72 weeks, which narrows the gap with tirzepatide's 15mg results considerably compared with the older 2.4mg ceiling.
The phrase "Wegovy equivalent to Mounjaro 15mg" is tempting shorthand, but there is no single answer. A 2.4mg Wegovy maintenance dose is not the clinical equivalent of 15mg Mounjaro; the 7.2mg approval brought semaglutide's results much closer to tirzepatide's ceiling. You can explore how Wegovy and Mounjaro compare overall, including mechanism, trial data and practical differences, if you want the fuller picture beyond the top dose.
The SURMOUNT-5 open-label trial, published in the New England Journal of Medicine in 2025, compared tirzepatide directly with semaglutide 2.4mg over 72 weeks in 751 adults with obesity and without diabetes. Tirzepatide produced greater average weight reduction. That trial used semaglutide at 2.4mg, not 7.2mg, so the head-to-head evidence at the very highest doses of each medicine remains limited. Our dedicated page on the 15mg Mounjaro and Wegovy comparison goes into the trial detail more carefully.
A comparison at the dose ceiling: what the numbers show
| Factor | Mounjaro 15mg (tirzepatide) | Wegovy 2.4mg (semaglutide) | Wegovy 7.2mg (semaglutide) |
|---|---|---|---|
| Mechanism | Dual GIP + GLP-1 receptor agonist | GLP-1 receptor agonist | GLP-1 receptor agonist |
| Average weight loss in trials | ~20–21% over 72 weeks (SURMOUNT-1) | ~15% over 68 weeks (STEP 1) | ~20.7% over 72 weeks |
| UK licensing (weight management) | BMI ≥30 or ≥27 + condition | BMI ≥30 or ≥27 + condition | BMI ≥30 only |
| Administration | Once-weekly subcutaneous injection (KwikPen) | Once-weekly subcutaneous injection | Once-weekly single-dose pen (approved 14 Apr 2026) |
| NICE recommendation | TA1026 (December 2024) | TA875 (March 2023, specialist services, max 2 years) | No separate NICE appraisal at time of writing |
Numbers cited from NICE TA1026 and the STEP 1 trial in the New England Journal of Medicine. The 7.2mg Wegovy approval is confirmed on GOV.UK's MHRA announcement.
Which one is right at this stage of treatment?
This question comes up a lot, including among people who order on a Monday morning before the week gets away from them, or who are planning ahead around a holiday when they won't want to start something new. The honest answer is that suitability at the 15mg tirzepatide level, or at the Wegovy ceiling, is a clinical call that depends on your full medical history, any conditions you're managing, how you've responded to treatment so far, and what your prescriber thinks is the right next step.
Side effects at higher doses tend to be GI-led for both medicines: nausea, changes in appetite, and digestive discomfort are reported most often. These typically settle after the first few weeks at a new dose level, though the pattern varies person to person. Our prescribers look at tolerability alongside weight outcomes when reviewing any dose decision.
If you've been prescribed tirzepatide elsewhere and want to understand how your current dose sits relative to Wegovy, the Mounjaro-to-Wegovy dose conversion page covers what can and can't be translated directly. And if cost at the top of the dose range is part of the picture, the cost comparison between Wegovy and Mounjaro is worth reading. Our clinical team reviews every consultation personally before any treatment is confirmed. Which medicine suits you at this stage is a decision our prescribers make with you, not for you.
Looking to start your weight loss journey?
Take a quick eligibility quiz to explore your options and see how we can support you.