Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow a Mounjaro-to-Wegovy switch works in practice, step by step
Step 1: understand why you are considering the switch
A question our prescribers hear most weeks is some version of: "I've been on Mounjaro for a few months, can I just try Wegovy instead?" The reasons vary. Sometimes it is cost. Sometimes it is a supply issue. Sometimes a patient has read about Wegovy's longer track record and wants to explore it. Each reason has a different clinical implication, so it is worth being clear about yours before the conversation starts.
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, the only one of its kind licensed for weight management in the UK. Wegovy (semaglutide) acts on the GLP-1 receptor only. In the SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, tirzepatide produced greater average weight reduction than semaglutide 2.4mg over 72 weeks, which means switching from Mounjaro to Wegovy is not a straightforward upgrade, and could mean a different rate of progress. That is not a reason to rule it out; it is a reason to go in with accurate expectations. Your prescriber can help set those. See how the two medicines compare across the key clinical dimensions if you want the fuller picture before your consultation.
Supply disruptions are a legitimate, practical reason to switch, and your prescriber can factor current availability into their advice. What matters is that the switch is planned, not reactive.
Step 2: the clinical review before any change
A switch between GLP-1 medicines is not simply a matter of stopping one pen and starting another on the same day. The prescriber will typically want to know: how long you have been on Mounjaro, which dose you are currently on, what your weight trajectory looks like, and whether you have experienced any side effects that might affect suitability for semaglutide.
There is no universal washout requirement published in the UK SmPCs, but the prescriber will decide the appropriate timing based on your specific situation. They will also need to consider where to start you on Wegovy's dose ladder. Wegovy's licensed schedule begins at 0.25mg, escalating through 0.5mg, 1.0mg, 1.7mg, and up to 2.4mg, and now up to 7.2mg following the MHRA's approval of that higher maintenance dose in January 2026, with a dedicated single-dose pen approved in April 2026. Whether you start at the bottom or at an intermediate point is a clinical call. The practical steps for making the switch are covered in detail on a dedicated page if you want a deeper read before your appointment.
At nume, transfer patients provide evidence of their current treatment before any change is made, that is part of how we keep the process safe.
Step 3: what to expect after the switch
Some people find the transition smooth; others notice a difference in how the medicines feel. Semaglutide and tirzepatide share a broadly similar gastrointestinal side-effect profile (nausea, changes in appetite, some digestive disruption) but the intensity and pattern can differ between individuals switching from one to the other. This is partly because you are, in effect, starting a new medicine, and your body may respond differently to a single-pathway GLP-1 agonist after time on a dual agonist. The experience of switching between the two is explored further if you want to know what patients typically report.
Weight loss may continue, plateau, or slow depending on where you start on Wegovy's schedule relative to your Mounjaro dose. Clinical trial data for Wegovy at 2.4mg showed average reductions of around 15% over 68 weeks in the STEP 1 trial, published in the New England Journal of Medicine. The newer 7.2mg dose showed around 20.7% in trials, approaching tirzepatide's results at the highest dose. None of those figures are individual predictions, your prescriber will monitor your response and adjust accordingly. You can also read about switching back to Mounjaro from Wegovy if things do not go as expected.
Mounjaro vs Wegovy: a factual comparison
The table below covers the main clinical differences relevant to someone weighing up a switch. Numbers are sourced from published trial data and NICE appraisals; individual results vary.
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 receptor agonist | GLP-1 receptor agonist |
| Average weight loss in trials | ~20–21% at 15mg (SURMOUNT-1, NEJM) | ~15% at 2.4mg (STEP 1, NEJM); ~20.7% at 7.2mg |
| Head-to-head result | Greater average reduction vs semaglutide 2.4mg (SURMOUNT-5, NEJM 2025) | 7.2mg narrows the gap significantly |
| Licensed UK dose range | 2.5mg to 15mg, once weekly | 0.25mg to 7.2mg, once weekly |
| NICE recommendation | TA1026: BMI ≥35 + ≥1 comorbidity (private: BMI ≥30) | TA875: BMI ≥35 + ≥1 comorbidity, specialist service, max 2 years |
| Contraception note | Add a barrier method for 4 weeks at start and after each dose increase if on oral contraceptives | No equivalent evidence of reduced pill absorption |
Which suits you is a clinical decision our prescribers make with you. If you are also curious how either medicine compares to Ozempic, it is worth knowing that Ozempic is licensed for type 2 diabetes, not weight management, a distinction that matters when weighing up your options. For those wondering about an Ozempic-to-Mounjaro direction of travel, that question is answered separately. Our clinical team reviews every request before any change is made. Speak to our prescribers to start the process.
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