Mounjaro®
Starting from £179.99/mo
Start journey Learn moreThe factors that shape a switch from semaglutide to tirzepatide
Is switching actually the right question to ask?
Before thinking about logistics, it helps to get clear on why you're considering a change. Some people have been on semaglutide for months and feel their weight loss has plateaued. Others have read about the differences between semaglutide and tirzepatide and want to know whether a different mechanism might suit them better. A few are transferring from another provider and their current prescription happens to be semaglutide. All of these are legitimate reasons to raise with a prescriber. What a prescriber is looking for is whether a switch is clinically appropriate for you specifically, not just in principle.
The two medicines are not interchangeable in the way that, say, two brands of the same drug might be. Tirzepatide activates both GIP and GLP-1 receptors; semaglutide targets GLP-1 alone. That difference in mechanism means the tolerability profile, the titration schedule, and the evidence base are distinct. How Wegovy and Mounjaro compare in practice is something worth reading alongside this page if you're still forming a view.
There is no blanket rule that says a switch must happen at a particular point or after a specific number of months. The right moment depends on your individual response, your current dose, and your prescriber's assessment of the evidence you can provide.
What the clinical evidence says about tirzepatide after semaglutide
The headline trial data are relevant context here. In the SURMOUNT-1 study, tirzepatide produced an average body-weight reduction of around 20–21% over 72 weeks at the 15mg dose, as reported in the New England Journal of Medicine. The STEP 1 trial for semaglutide 2.4mg reported around 15% average reduction over 68 weeks. More directly, the SURMOUNT-5 open-label head-to-head trial (72 weeks, 751 adults with obesity) found tirzepatide produced greater average weight reduction than semaglutide 2.4mg, a finding cited in NICE's appraisal of tirzepatide (TA1026). The newer Wegovy 7.2mg dose narrows that gap, so the picture is not static.
The table below sets out the key factual differences to help you think about the decision.
| Factor | Semaglutide (Wegovy injection) | Tirzepatide (Mounjaro) |
|---|---|---|
| Mechanism | GLP-1 receptor agonist | Dual GIP + GLP-1 receptor agonist |
| Average weight loss (trial, highest dose) | ~15% at 2.4mg (STEP 1, 68 weeks) | ~20–21% at 15mg (SURMOUNT-1, 72 weeks) |
| UK licence for weight management | Yes (BMI ≥30, or ≥27 + condition) | Yes (BMI ≥30, or ≥27 + condition) |
| NICE-recommended for NHS use | TA875 (specialist services, max 2 years | TA1026) phased rollout from June 2025 |
| Black Triangle (▼) MHRA monitoring | Yes | Yes |
| Oral option available | Yes (Wegovy tablets, MHRA approved June 2026) | No (injection only) |
Numbers from SURMOUNT-1 (NEJM) and STEP 1 (NEJM); NICE TA1026 and TA875 for NHS recommendations.
What actually happens when you make the switch
Practically speaking, going from semaglutide to tirzepatide is not a straight dose-for-dose swap. Tirzepatide has its own titration ladder, starting at 2.5mg, a starter dose designed to let your system adjust, not to deliver immediate therapeutic effect. Your prescriber will decide where to begin based on the dose of semaglutide you were taking and how you've been getting on with it.
There is also a question of timing. Some prescribers prefer a short gap between stopping one medicine and starting another; others are comfortable with a more direct transition. This is one of those details the Patient Information Leaflet and your prescriber's clinical judgement have to resolve for your situation, not a general rule a content page can set.
If you're thinking about moving from semaglutide to tirzepatide and you're already a patient elsewhere, a transfer patient consultation at nume involves checking your current treatment evidence before any prescription is issued. It's the same process as a new patient assessment, with that extra step added. Our clinical team's approach to this is described on our prescribers' profile page.
Side effects at the point of switching are worth flagging too. GI symptoms (nausea, loose stools, reflux) are common early on with both medicines and may resurface when you restart at the bottom of a new titration schedule, even if you'd settled on semaglutide. That's normal, but it's something to be prepared for and to discuss with your prescriber if they become difficult to manage. It's also worth reading about how tirzepatide and semaglutide can affect facial fat loss, as some people find this a useful consideration when weighing up a change.
The practical next step
If you've decided the switch is worth exploring, the route through nume (sorry, through a registered online pharmacy like ours) is a free consultation. There's no obligation at that point; it's a clinical assessment, and if the prescriber concludes that tirzepatide isn't suitable for you right now, they'll tell you why. You can read more about how the changeover works before you start, or go straight to the consultation page if you're ready.
Which medicine suits you is not something a comparison page can determine. That's a clinical decision our prescribers make with you, taking your full health history into account.
Looking to start your weight loss journey?
Take a quick eligibility quiz to explore your options and see how we can support you.