Thinking about switching from Mounjaro to Wegovy?

What the head-to-head trial data actually shows

The most direct evidence comes from SURMOUNT-5, a 72-week open-label trial involving 751 adults with obesity and no diabetes, which compared tirzepatide (Mounjaro) against semaglutide 2.4mg (Wegovy) head-to-head. Tirzepatide produced meaningfully greater average weight reduction. NICE's appraisal of tirzepatide referenced this indirect and direct comparison evidence when recommending it for NHS use in December 2024, noting results that placed it ahead of semaglutide at standard maintenance doses.

The picture shifted slightly when Novo Nordisk introduced a higher-dose option. The MHRA approved the dedicated single-dose Wegovy 7.2mg pen in April 2026; trials at that dose reported around 20.7% average weight loss over 72 weeks, which narrows the gap with tirzepatide 15mg considerably. So the comparison you're making today is not quite the same one that existed a year ago.

If you have been doing well on Mounjaro and are asking whether Wegovy might do better, the honest answer from the current data is: probably not, on average. If you are asking because you cannot tolerate Mounjaro, that is a different question entirely — and one worth putting to a prescriber rather than resolving by comparison table alone.

The practical differences that matter when switching

Mechanism is the clearest distinction. Mounjaro activates two receptors (GIP and GLP-1) making it the only dual-agonist weight-loss medicine currently licensed in the UK, as the NHS tirzepatide page explains. Wegovy targets GLP-1 only. Whether that additional pathway translates to better tolerability or results for a given individual is something a prescriber weighs against your profile.

The table below sets out the key factual differences.

One practical note: if you are on oral contraception and considering a switch back to Mounjaro after a spell on Wegovy, the absorption-interaction guidance differs. NHS England advises that women using oral contraceptives add a barrier method for the first four weeks of tirzepatide and for four weeks after each dose increase, because Mounjaro can slow pill absorption. No equivalent interaction is flagged for semaglutide. Worth raising with your prescriber, especially if a switch coincides with a new pack of pills.

When switching from Wegovy to Mounjaro might be the question instead

The search sometimes runs the other way. Patients who started on semaglutide (perhaps through an earlier private prescription or via an NHS specialist service) sometimes ask whether moving to tirzepatide makes sense, particularly now that NICE has recommended it and private access has widened. The trial data suggests tirzepatide produces stronger average results; the SURMOUNT-5 findings are the clearest evidence to date. But switching medicines means restarting titration, managing a new tolerability profile and, depending on where you are in your treatment, potentially losing momentum you have already built.

Some people find semaglutide's side-effect profile easier to manage; others find tirzepatide more agreeable. Neither answer is universal. A prescriber reviewing your current dose, weight trajectory and recent side-effect history can give a more useful steer than any general comparison. Timing matters too, switching mid-dose just before a holiday or in the week after payday when you want stability is rarely ideal. Think about your next four to eight weeks before initiating a change.

If you want to explore the practicalities of moving from Mounjaro to Wegovy, or understand the cost difference between the two, those details are worth looking at alongside the clinical question. The full Wegovy vs Mounjaro comparison on the site covers eligibility, mechanism and NICE guidance in more depth.

How a switch is handled through a regulated prescriber

Switching between licensed weight-loss medicines is not something you can do by simply ordering the other pen. A prescriber needs to see where you are: your current dose, how long you have been on it, your weight at the point of switch, and any side effects that prompted the question. At nume, every order (including a switch request) is reviewed by a GPhC-registered Independent Prescriber before anything is dispatched. There are no automated approvals. Evidence of your current treatment is checked; a dose increase or medicine change is only progressed where the clinical picture supports it.

The process is straightforward. You complete a free consultation; a prescriber reviews it the same day; if a switch is clinically appropriate, your new treatment is dispatched the same working day on orders placed before 12pm, arriving the next working day by DPD. Our clinical team is available seven days a week for aftercare questions during any transition period. If you are unsure whether to make the change at all, detailed guidance on the switching process may help you frame the question before your consultation. You can also read more about how nume works before starting. Which medicine suits you is a clinical decision our prescribers make with you, not for you.