Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow a Wegovy-to-Mounjaro switch works in practice, and how the two treatments compare
Step 1: understanding why people switch, and whether it makes clinical sense
The most common reasons a prescriber might consider moving someone from Wegovy to Mounjaro are plateau weight loss, tolerability issues with semaglutide, or simply wanting to try the medicine with the stronger head-to-head trial results. In the SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, tirzepatide produced greater average weight reduction than semaglutide 2.4mg over 72 weeks in adults with obesity who did not have diabetes. That evidence matters when a conversation about switching comes up.
What a switch is not is a quick fix. If Wegovy has stopped working, the reason is worth exploring first. Has the dose reached its ceiling? Has lifestyle drifted? A prescriber at nume will look at your full treatment history before recommending a change, because switching medicines without that review risks restarting from scratch unnecessarily. You can read more about the broader question of what switching between these treatments actually achieves on our detailed explainer.
One practical check you can do right now, in under a minute: look at the dose you are currently on and note whether you have reached Wegovy's standard maintenance dose of 2.4mg. If you have not, your prescriber may want to exhaust that option before a switch. That single piece of information shapes the whole conversation.
Step 2: the mechanics of moving from semaglutide to tirzepatide
Wegovy contains semaglutide, a GLP-1 receptor agonist. Mounjaro contains tirzepatide, which activates both GLP-1 and GIP receptors. The dual-pathway mechanism is what sets Mounjaro apart, and it is partly why the trial results differ. You can explore that biological distinction in detail on our semaglutide vs tirzepatide mechanism page.
When switching, a prescriber will typically start tirzepatide at its 2.5mg dose rather than matching whatever semaglutide dose you were on. The 2.5mg starting dose exists to let your system adjust to a new medicine and a new receptor pathway. It is not a therapeutic ceiling; it is an adjustment period. Jumping to a higher dose on day one increases the risk of GI side effects that might otherwise have been avoided with a more gradual approach. Titration then proceeds in steps, guided by the prescriber reviewing how you are tolerating each level.
There is no medically mandated washout period between the two medicines that applies in all cases, but the timing of the last Wegovy dose relative to the first Mounjaro dose is something your prescriber will consider individually. Do not attempt to manage this overlap yourself. The free consultation at nume is the right place to have that conversation.
Step 3: comparing Wegovy and Mounjaro side by side
Both medicines share a broadly similar side-effect profile because they both activate GLP-1 receptors. Nausea, loose stools, constipation, indigestion and reduced appetite are common to both, particularly at the start or after a dose increase. The NHS medicines pages for tirzepatide and semaglutide set out the full lists clearly. What differs is the magnitude of weight loss seen in trials and the additional GIP action of tirzepatide.
| Factor | Wegovy (semaglutide) | Mounjaro (tirzepatide) |
|---|---|---|
| Mechanism | GLP-1 receptor agonist | Dual GLP-1 and GIP receptor agonist |
| Licensed UK doses | 0.25mg to 2.4mg (and 7.2mg, approved Apr 2026) | 2.5mg to 15mg |
| Average weight loss (trial) | ~15% at 2.4mg over 68 weeks (STEP 1, NEJM) | ~20–21% at 15mg over 72 weeks (SURMOUNT-1, NEJM) |
| Head-to-head evidence | Compared in SURMOUNT-5 (2025) | Greater average reduction in SURMOUNT-5 |
| NICE recommendation | TA875 — specialist services, max 2 years | TA1026 — BMI ≥35 plus ≥1 comorbidity |
| Injection frequency | Once weekly | Once weekly |
These numbers come from controlled trial populations and should be read as population averages, not individual predictions. The full Wegovy vs Mounjaro comparison on our site goes deeper into the evidence if you want more detail before your consultation.
What the clinical decision actually looks like
Which medicine suits you is not a question the trial data alone can answer. Your medical history, any medicines you are already taking, how you responded to Wegovy, and your current BMI and comorbidities all factor in. The NICE appraisal for tirzepatide (TA1026) sets out the population it was evaluated in; a prescriber applies that to your specific picture.
At nume, a named clinician reads every consultation the same day. There is no algorithm making prescribing decisions. If a switch to Mounjaro is appropriate, the prescriber will confirm it, set the starting dose, and explain what to watch for. If it is not the right move yet, you will hear why. People who have already been through this decision in the other direction may find the reverse switch page useful context, and if you are considering switching from Ozempic to Mounjaro our dedicated guide walks through how that process typically works. Those who have previously used Mounjaro and want to understand switching back to Mounjaro from Wegovy will find a full clinical overview there too. Our clinical team profile at Mostafa Damghani gives a clearer picture of who is reviewing your case. There is no subscription at nume, and no repeat is issued without a fresh clinical review. That structure exists because dose changes and treatment switches carry real clinical weight.
Ready to talk it through? Speak to our prescribers and get a same-day assessment of whether switching is right for you.
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