Mounjaro®
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Start journey Learn moreThe Mounjaro-to-Wegovy decision: what actually tips the balance
Why someone on Mounjaro would even consider switching at maintenance
If you've reached a stable weight on Mounjaro and you're wondering whether Wegovy could hold that result just as well, you're not alone. It's a question our prescribers hear regularly, and the motivation is usually practical: Wegovy may be more accessible through certain services, or a prescriber transition means a new review is needed. Sometimes tolerance shifts over time, and what worked during active weight loss feels different once you're trying to maintain rather than reduce.
Maintenance is a different clinical phase. The goal is no longer maximum weight reduction but keeping the results you've worked for, ideally at the lowest effective dose that achieves that. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist; Wegovy (semaglutide) acts on the GLP-1 pathway alone. That single difference in mechanism can translate to a real-world difference in how much weight each medicine helps sustain — something worth taking seriously before swapping.
The SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, found tirzepatide produced greater average weight reduction than semaglutide 2.4mg over 72 weeks in adults with obesity and no diabetes. That head-to-head result is relevant context when you're weighing the maintenance picture. The NICE appraisal of tirzepatide (TA1026) references these comparisons in its committee discussion.
How the two medicines compare side by side
Before the decision can be framed properly, it helps to see the key clinical differences laid out plainly.
| Feature | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 agonist | GLP-1 agonist only |
| Trial weight loss at highest dose | ~20–21% at 15mg (SURMOUNT-1, NEJM) | ~15% at 2.4mg (STEP 1, NEJM); ~20.7% at 7.2mg (MHRA, 2026) |
| Licensed UK maintenance strengths | Up to 15mg weekly | Up to 7.2mg weekly (MHRA-approved April 2026) |
| NICE recommendation threshold | BMI ≥35 + ≥1 comorbidity (TA1026) | BMI ≥35 + ≥1 comorbidity, specialist services, max 2 years (TA875) |
| Side-effect profile | GI-led; also affects oral contraceptive absorption at dose changes | GI-led; no equivalent evidence of oral contraceptive effect |
Sources: NHS tirzepatide medicine page; NICE TA875 (semaglutide). Numbers are from clinical trial populations and individual results vary.
The full Wegovy vs Mounjaro comparison on this site covers the clinical picture in more depth. If cost is part of your thinking, the UK price comparison sets out what's involved.
What a prescriber weighs when reviewing a switch request
A switch from Mounjaro to Wegovy isn't just a dose-conversion exercise. Your prescriber will want to know how much weight you lost, at what dose you've stabilised, how long you've been at maintenance, and whether side effects or other factors are driving the question. They'll also look at whether you've had previous experience with semaglutide, either Wegovy or Ozempic (though Ozempic is licensed for type 2 diabetes, not weight loss, so the comparison there is limited).
Dose equivalence between the two medicines isn't a fixed table. The dose conversion guide explains why a one-to-one mapping doesn't exist. A prescriber typically starts the new medicine at a lower dose and titrates, even for someone experienced with GLP-1 therapy, because tolerability can differ. If you've been on Mounjaro and are curious about the transition from the other direction, the Wegovy-to-Mounjaro pathway covers how that usually works too.
Women using oral contraceptives should be aware that tirzepatide can reduce pill absorption during dose changes, a non-oral method is recommended for the first four weeks of treatment and four weeks after any dose increase. NHS England notes no equivalent evidence of this effect for semaglutide. If switching to Wegovy removes that complication, it may genuinely matter to some patients. The NHS England guidance on weight-management injections covers this and other practical considerations.
Which is better for keeping weight off, and who decides?
Trial data suggests tirzepatide produces greater average weight loss, and there's reasonable logic that a medicine with a stronger loss signal may also be better at holding the result. But maintenance is under-studied compared to active treatment phases, and individual responses vary enough that aggregate trial figures are a starting point, not a verdict.
Wegovy at 7.2mg (approved in the UK on 14 April 2026) narrows the gap with tirzepatide's top dose considerably. If you're already well-established on Mounjaro at a moderate dose and maintaining comfortably, switching for its own sake may not be clinically indicated. If there are clear reasons (tolerability, access, cost, a prescriber transition) then the switch is worth a proper review.
Our prescribers assess this individually. If you'd like to explore your options, including whether switching makes clinical sense for your situation, starting a free consultation is the right first step. You can also read more about how Wegovy performs specifically in a post-Mounjaro maintenance context, or about how the switch itself is typically managed. Which medicine suits your maintenance phase is a clinical decision our prescribers make with you.
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