Switching to Wegovy After Mounjaro: a clear clinical picture

You've been on Mounjaro for a while (here's where the two medicines part ways

Picture this: you've worked up to a maintenance dose of Mounjaro, things have been going reasonably well, but for some reason) availability, cost, a clinical decision with your prescriber, switching to Wegovy is on the table. Before that happens, it helps to understand why these aren't interchangeable pens.

Mounjaro (tirzepatide, made by Eli Lilly) activates two gut-hormone receptors simultaneously: GIP and GLP-1. Wegovy (semaglutide, made by Novo Nordisk) targets GLP-1 alone. That dual action is why tirzepatide tends to produce somewhat greater average weight loss in head-to-head evidence: the SURMOUNT-1 trial published in the New England Journal of Medicine showed around 20–21% average body-weight reduction at the highest dose over 72 weeks, while STEP 1, the equivalent semaglutide trial, reported around 15% over 68 weeks at 2.4 mg. A more direct comparison comes from the SURMOUNT-5 trial (2025), which found tirzepatide produced greater average weight loss than semaglutide 2.4 mg in a head-to-head setting among adults with obesity and without diabetes. The gap narrows with Wegovy's newer 7.2 mg dose, approved by the MHRA in January 2026, which reached around 20.7% in trials, but that's still a different pharmacological starting point than the medicine you'd be leaving.

For a fuller side-by-side breakdown of the two medicines, the Wegovy vs Mounjaro comparison covers their mechanisms, trial results and licensed eligibility in detail.

The practical question: what actually happens at the point of switching

This is the part most people searching this topic genuinely want answered. When you stop Mounjaro and start Wegovy, you are not continuing at an equivalent dose, you are starting Wegovy's own titration schedule from the beginning. That means starting at 0.25 mg weekly and working up through 0.5, 1.0, 1.7 and 2.4 mg over roughly five months, or further to 7.2 mg if that dose is clinically appropriate for you. Your body has been accustomed to tirzepatide's dual mechanism; moving to a single-receptor agonist is a genuine pharmacological change, not simply swapping one pen for another.

There is no official published washout protocol specifically for this switch in UK prescribing guidance, which is part of why prescriber judgement matters here. Some clinicians prefer a short gap to reduce overlapping GI effects; others move patients across directly. Neither approach is wrong in principle, the right one depends on your individual history, how you tolerated Mounjaro, and your current dose. If you want to explore what the switch might look like in your specific situation, the clinical detail on switching from Mounjaro to Wegovy goes deeper into the prescriber considerations.

One thing our prescribers hear fairly often: people worry that starting Wegovy at 0.25 mg after a high Mounjaro dose means going backwards. It feels counterintuitive. The titration steps exist for tolerability, not because the earlier doses are less serious, and moving through them can go faster if your system is already accustomed to a GLP-1 mechanism, though that is a clinical call, not something to self-manage.

How the two medicines compare side by side

The table below summarises the key factual differences. Numbers are cited from the sources noted; individual results vary and a prescriber reviews what applies to you.

For cost context alongside efficacy, the tirzepatide vs semaglutide cost comparison sets out what private treatment typically involves financially for each medicine.

Whether switching makes sense, and how that decision gets made

There are legitimate reasons a prescriber might recommend moving from Mounjaro to Wegovy: persistent side effects that seem mechanism-specific, stock considerations, or a clinical preference for semaglutide's longer evidence base in certain patient profiles. There are also reasons it might not be the right move, particularly if Mounjaro is working well and the motivation is cost alone. The fuller guide to Wegovy after Mounjaro covers the clinical rationale in more detail, and if you're curious about the reverse journey, the question of returning to Mounjaro after Wegovy is also addressed separately, as is whether taking Mounjaro after Wegovy is clinically appropriate.

What matters most is that the decision is made with evidence in front of a prescriber who knows your history, not by comparing Reddit threads. Both medicines are covered under nume's weight-loss treatment consultations, where a GPhC-registered Independent Prescriber reviews your case personally. If you're partway through Mounjaro and want to discuss whether Wegovy is a better fit going forward, our treatment overview explains the full picture. For background on how our clinical team approaches these decisions, the clinical team profile is worth a read. Which medicine suits you is a decision our prescribers make with you, not one we'd ever reduce to a league table.