Mounjaro®
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Start journey Learn moreThe factors that shape a Wegovy-to-tirzepatide switch, and how a prescriber works through them with you
Why people consider switching, and what the evidence actually says
Most people reading this are either dissatisfied with the weight loss they've achieved on semaglutide, or they've read about tirzepatide's trial results and want to understand the difference. Both reactions are completely reasonable. Progress plateauing after several months on Wegovy is genuinely frustrating, especially when you've made real changes to how you eat and move.
The clinical picture is this: tirzepatide (sold in the UK as Mounjaro) activates two gut-hormone pathways, GIP and GLP-1, where semaglutide targets GLP-1 alone. In SURMOUNT-1, participants at 15mg tirzepatide lost an average of around 20–21% of body weight over 72 weeks, as reported in the NEJM trial paper. The SURMOUNT-5 head-to-head then compared tirzepatide directly against semaglutide 2.4mg and found tirzepatide produced greater average loss. That said, NICE's appraisal of tirzepatide notes these comparisons are indirect outside of SURMOUNT-5, and individual responses vary considerably.
Switching is not simply swapping one pen for another. There is a washout and restart process, and the dose you begin on tirzepatide is unlikely to match the dose you were at on Wegovy, and our page on what to expect when switching from semaglutide to tirzepatide walks through what that involves. A prescriber familiar with both medicines works through that translation with you, which is precisely why a clinical review before any switch is required, not optional. You can read more about the broader comparison between the two on the Wegovy vs Mounjaro page.
How Wegovy and Mounjaro compare on the key practical points
A side-by-side look at the facts most people ask about:
| Factor | Wegovy (semaglutide 2.4mg) | Mounjaro (tirzepatide, up to 15mg) |
|---|---|---|
| Mechanism | GLP-1 receptor agonist | Dual GIP + GLP-1 receptor agonist |
| Average weight loss (pivotal trial) | ~15% over 68 weeks [STEP 1, NEJM] | ~20–21% over 72 weeks [SURMOUNT-1, NEJM] |
| UK weight-management licence | BMI ≥30, or ≥27 with a weight-related condition | BMI ≥30, or ≥27 with a weight-related condition |
| NICE recommendation | TA875 (via specialist weight management services, max 2 years | TA1026) BMI ≥35 with ≥1 comorbidity (lower thresholds for some ethnic backgrounds) |
| Starting dose on switch | N/A (you are switching away) | Prescriber-determined; typically retitrated from a lower dose |
| Common side effects | GI-led: nausea, diarrhoea, constipation, reflux | GI-led: similar profile; tolerability varies individually |
Source: NICE TA1026 (tirzepatide); NICE TA875 (semaglutide/Wegovy); NEJM SURMOUNT-1 and STEP 1 trials. Trial figures are population averages; individual results differ.
It is worth noting that Ozempic, though also semaglutide, is licensed for type 2 diabetes, not weight loss. If you are considering switching from Ozempic rather than Wegovy, that is a different clinical conversation; our page on switching from Ozempic to tirzepatide covers that distinction.
What the switching process looks like in practice
There is no standard published UK protocol that maps a specific Wegovy dose to a specific tirzepatide starting dose. What prescribers do instead is assess where you are: how long you've been on semaglutide, your most recent dose, how you've tolerated it, your current weight and any relevant health history. From there, most clinical approaches involve starting tirzepatide at a lower dose and retitrating upward, rather than jumping straight to the dose you were aiming for. The detail of that process is explored on our switching from semaglutide to tirzepatide dosing page.
The NHS summarises both medicines' side-effect profiles on its patient-information pages for tirzepatide and semaglutide. The GI side effects (nausea, loose stools, reflux) are broadly similar between the two medicines, though their severity and timing can differ when you restart at a lower dose. Some people find the transition easier than they expected; others need a slower titration. A prescriber tracks that with you.
If you've been on tirzepatide and are curious about the reverse journey, the switching from Mounjaro to Wegovy page covers what that involves.
Which medicine is right depends on the clinical picture, not the trial headline
Tirzepatide's trial results are compelling, and it is the only dual GIP/GLP-1 receptor agonist licensed for weight management in the UK. But better average results in a population don't automatically translate into the better choice for a specific person. Contraindications, current medications, how your body handled semaglutide, your BMI trajectory and any other health conditions all feed into a prescriber's thinking.
This is the core of how we work at nume. Our clinical team (you can read about our clinical oversight on the clinical team page) personally reviews every consultation. If you're transferring from another provider, we review evidence of your current treatment before any prescription is issued. No dose is changed, and no switch is made, on assumption alone.
If you're exploring your options more broadly, the weight-loss treatment overview sets out what we offer. And if a cost comparison is part of your thinking, the Wegovy vs Mounjaro cost comparison page gives an honest read on what the price difference looks like. Which medicine suits you is a clinical decision our prescribers make with you, the consultation is where that conversation starts.
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