Mounjaro®
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Start journey Learn moreHow the peak doses of Mounjaro and Wegovy compare on weight loss, mechanism and eligibility
You've reached the top of the titration ladder, now what?
Picture this: you've been on Mounjaro for six months, you've worked through the earlier doses, and your prescriber is considering 15mg. Or you're switching from Wegovy 2.4mg and want to understand what changes. Either way, the question people ask most often at this point is whether the two medicines are broadly equivalent at their highest licensed doses.
The short answer is no, not in a strict pharmacological sense. Mounjaro (tirzepatide) activates both the GIP and GLP-1 receptors, while Wegovy (semaglutide) targets GLP-1 alone. That structural difference means the two medicines cannot be converted dose-for-dose the way, say, two versions of the same antibiotic might be. What dose equivalence guidance actually gives you is a clinical starting point, not a mathematical rule.
At the highest doses, the trial evidence does converge in one sense: both produce clinically meaningful weight loss for many people. The SURMOUNT-1 trial recorded an average body-weight reduction of around 20–21% over 72 weeks at tirzepatide 15mg, in adults without diabetes. The STEP 1 trial for semaglutide 2.4mg recorded around 15% average reduction over 68 weeks in a comparable group. Those figures come from different trial designs and should not be read as a direct contest; still, they give both medicines a strong evidence base, as set out in NICE's technology appraisal TA1026 for tirzepatide and TA875 for semaglutide.
For a fuller picture of how the conversion question sits across the entire dose range, the Mounjaro to Wegovy dose conversion guide covers the clinical thinking in more detail.
What the head-to-head trial actually showed
In 2025 the SURMOUNT-5 trial published results that changed the conversation. It was an open-label, 72-week study involving 751 adults with obesity and no diabetes, comparing tirzepatide directly against semaglutide 2.4mg. Tirzepatide produced greater average weight reduction. The study was published in the New England Journal of Medicine and was one of the evidence sources considered in NICE TA1026's committee deliberations.
Before those results arrived, indirect comparisons already suggested tirzepatide had an edge at its highest dose. SURMOUNT-5 made that comparison more concrete. But there is an important caveat: SURMOUNT-5 compared tirzepatide against the 2.4mg dose of Wegovy. The MHRA approved a higher 7.2mg Wegovy dose in early 2026, and a dedicated single-dose 7.2mg pen was cleared on 14 April 2026, with trial data suggesting around 20.7% average weight loss over 72 weeks at that dose. That narrows the gap with tirzepatide 15mg considerably. Specific dose or pen availability is always confirmed at consultation, because supply and clinical suitability both play a role.
The comparison between Wegovy and Mounjaro has therefore moved since the original trial data, and it will likely keep evolving as longer-term data accumulates.
Comparing the highest doses side by side
| Factor | Mounjaro 15mg (tirzepatide) | Wegovy 2.4mg (semaglutide) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 receptor agonist | GLP-1 receptor agonist |
| Average weight loss in trials | ~20–21% over 72 weeks (SURMOUNT-1, NEJM) | ~15% over 68 weeks (STEP 1, NEJM) |
| Head-to-head result | Greater average loss vs semaglutide 2.4mg (SURMOUNT-5, NEJM 2025) | 7.2mg dose (~20.7% over 72 weeks) narrows the gap |
| Administration | Once-weekly subcutaneous injection (KwikPen) | Once-weekly subcutaneous injection (pre-filled pen) |
| Storage | Refrigerated 2–8°C; see SmPC for room-temperature window | Refrigerated 2–8°C; see SmPC for room-temperature window |
| UK licence for weight management | Yes (MHRA; Black Triangle ▼) | Yes (MHRA; Black Triangle ▼) |
Storage matters more than it sounds in practice. Both pens live in the fridge (most people put them in the door shelf) and both have a limited window for room-temperature use that you should check in the Patient Information Leaflet rather than rely on any general figure online.
If you're looking specifically at a lower point in the titration, the 10mg Mounjaro comparison or the 5mg comparison may be more relevant to where you are right now.
Which is right for you, and what a prescriber actually considers
Trial averages are population figures. What matters for any individual is their medical history, current medications, any relevant conditions, and how they've responded to treatment so far. A prescriber reviewing your case at 15mg Mounjaro is asking different questions than one deciding whether to start you on Wegovy.
Eligibility for both medicines in a private setting follows the licensed criteria: broadly, adults with a BMI of 30 or above, or 27 and above with a weight-related condition such as hypertension or type 2 diabetes. BMI alone does not determine approval; the whole clinical picture does. Lower thresholds apply for some ethnic backgrounds under UK guidance, your prescriber will work through this with you.
Cost is a factor too, and it's worth understanding the context. Eli Lilly raised Mounjaro's UK list price from September 2025, and tirzepatide now typically sits at a higher price point than semaglutide across most private providers. The reason Wegovy tends to cost less than Mounjaro at equivalent stages reflects both manufacturer pricing and the single-receptor mechanism. That gap does not mean one medicine is better value on clinical grounds.
At nume, sorry, at nume, our prescribers review every consultation personally, the same day you submit it. Which medicine, which dose, whether to continue or adjust: those are clinical decisions made with you, not for you. Start your free consultation and find out which treatment fits your situation.
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