Switching from Mounjaro to Wegovy: a step-by-step guide

Step 1 — understanding why you might switch (and the misconception worth clearing up)

A common assumption is that switching to Wegovy from Mounjaro means stepping down to a less effective medicine. The evidence doesn't quite support that framing. Head-to-head data from the SURMOUNT-5 trial, published in the New England Journal of Medicine (2025), did show tirzepatide producing greater average weight reduction than semaglutide 2.4mg over 72 weeks. But reasons to switch are rarely about chasing the biggest number on a chart. Tolerability, supply availability, clinical history, other medicines, and how your body has responded all shape the decision. Some people find the GLP-1-only profile of semaglutide sits better with them; others are advised to switch for clinical reasons their prescriber has identified. Neither medicine suits everyone equally, and a switch in either direction is a legitimate clinical option.

Step 2, what the two medicines are and where they differ

Mounjaro (tirzepatide, made by Eli Lilly) activates both GIP and GLP-1 receptors, making it the only dual-agonist weight-loss medicine currently licensed in the UK. Wegovy (semaglutide, made by Novo Nordisk) targets GLP-1 receptors only. Both slow gastric emptying and reduce appetite; both are once-weekly subcutaneous injections. The dose structures, however, are distinct. Mounjaro runs from 2.5mg up to 15mg across six steps. The Wegovy injection runs from 0.25mg through 0.5mg, 1mg, 1.7mg and up to 2.4mg as standard maintenance, with a higher 7.2mg dose now approved by the MHRA following the dedicated single-dose 7.2mg pen's approval in April 2026. There is no simple conversion chart that maps one medicine's dose onto the other's; a prescriber sets the starting point for the new medicine based on your full clinical picture. The comparison below sets out the headline differences factually.

Both medicines carry a Black Triangle (▼) status with the MHRA, meaning they are subject to additional monitoring. You can find detailed side-effect and dosing information on the NHS semaglutide medicines page and the Mounjaro equivalent.

Step 3, the clinical process for making the switch safely

There is no universal washout protocol published for switching between these two medicines, and guidance in this area is still evolving. In practice, prescribers weigh several factors: which dose of Mounjaro you're currently on, how well tolerated it has been, your weight-loss trajectory, and any comorbidities. Most clinicians do not simply stop tirzepatide one week and start semaglutide the next without planning the transition; the starting dose of semaglutide is typically set conservatively given some overlap in GI-related side-effect risk during the adjustment period. If you're also on oral contraception, the NHS England guidance on weight-management injections and contraception is worth reading: tirzepatide in particular may reduce absorption of the pill, and your prescriber needs to know your full medication list before and after any switch. Every switch at nume is reviewed by a named prescriber before anything is dispensed.

Step 4, deciding whether a switch is right for you

Which medicine suits you is a clinical decision made with our prescribers, not a choice made from a comparison table. If you're coming to nume from another service, or considering switching direction, our guide to switching to Wegovy covers the broader context, and you can explore everything about Wegovy as a treatment before your consultation. Patients who've previously been on Saxenda will find that our Saxenda-to-Wegovy switching guide explains what that change involves in practice. If your previous treatment was the liraglutide formulation specifically, our page on moving from liraglutide to semaglutide covers how those two medicines compare and what the transition typically looks like. Patients who've previously been on Ozempic should note that Ozempic is licensed for type 2 diabetes rather than weight management; our Ozempic-to-Wegovy switching page explains the distinction clearly. If you're curious about what options exist beyond semaglutide, the semaglutide-to-retatrutide comparison outlines emerging alternatives. To check whether you're eligible to start or switch treatment through nume, check your eligibility via a free consultation, reviewed the same day by one of our clinical team.