Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow the doses and evidence line up when switching between these two medicines
What SURMOUNT-5 and STEP 1 tell us about where the doses sit relative to each other
The most rigorous way to think about a semaglutide-to-tirzepatide conversion is through the trial data rather than through dose numbers alone, because milligrams are not directly interchangeable between the two drugs.
In SURMOUNT-5 (NEJM, 2025), adults with obesity but without diabetes lost an average of around 20–21% of body weight on tirzepatide 15mg over 72 weeks. The STEP 1 trial, also 72 weeks, reported roughly 15% average reduction on semaglutide 2.4mg. That gap is meaningful, though the populations and protocols differed. The NICE appraisal of tirzepatide (TA1026) notes that indirect comparisons consistently favour tirzepatide, while acknowledging the limitations of cross-trial comparison.
The practical implication: when a prescriber considers moving someone from Wegovy to Mounjaro, they are not looking for a dose that produces an identical blood-level match. They are looking at where you are in your Wegovy schedule, how you have tolerated it, and what therapeutic goal makes sense, and our full guide to Wegovy v Mounjaro sets out how those factors influence the decision in detail. A person finishing their first few months on 1mg semaglutide will be assessed differently from someone who has been on 2.4mg for a year.
The Wegovy 7.2mg single-dose pen, approved by the MHRA on 14 April 2026, narrows the efficacy gap somewhat: trials reported around 20.7% average weight loss over 72 weeks at that higher maintenance dose, which approaches tirzepatide 15mg results. That matters for a semaglutide-to-Mounjaro conversion chart because the landscape changed again in 2026.
| Feature | Wegovy (semaglutide injection) | Mounjaro (tirzepatide) |
|---|---|---|
| Mechanism | GLP-1 receptor agonist | Dual GIP and GLP-1 receptor agonist |
| Licensed UK maintenance dose | 2.4mg weekly (7.2mg pen from Apr 2026) | Up to 15mg weekly |
| Average weight loss in trials | ~15% at 2.4mg (STEP 1); ~20.7% at 7.2mg | ~20–21% at 15mg (SURMOUNT-1) |
| Titration steps | 0.25 → 0.5 → 1.0 → 1.7 → 2.4mg (~4-weekly) | 2.5 → 5 → 7.5 → 10 → 12.5 → 15mg (~4-weekly) |
| UK licence for weight management | BMI ≥30, or ≥27 with a weight-related condition | BMI ≥30, or ≥27 with a weight-related condition |
| Injection frequency | Once weekly | Once weekly |
What a real Mounjaro-to-Wegovy conversion looks like in practice
Clinicians switching patients between these medicines typically restart at the beginning of the new drug's titration schedule rather than jumping to a dose that looks numerically similar. The receptors involved are different, the absorption profiles differ, and tolerance built up on semaglutide does not transfer directly to tirzepatide, or vice versa.
If you are asking about a mounjaro-to-wegovy conversion chart because you are considering the switch in that direction, the same principle applies. A prescriber will usually suggest starting Wegovy at 0.25mg regardless of the Mounjaro dose you were on, titrating upward as tolerated. That can feel counterintuitive if you have been on a higher Mounjaro dose for months. The logic is safety: each medicine's GI side-effect profile needs fresh tolerance-building at the lower doses.
One simple check you can do in under a minute: look up whether the pharmacy you are considering is on the GPhC pharmacy register before handing over any medical history. It takes seconds and tells you whether the service is regulated. For reference, you can verify nume's own GPhC registration at registration number 9012878.
For a detailed look at how the switch works step by step, our guide to converting from Mounjaro to Wegovy covers the practicalities, including what to tell your prescriber and what to expect during re-titration. If you are moving in the other direction, our guide to converting from Mounjaro to Wegovy walks through each stage of that process, from your final tirzepatide dose through to restarting semaglutide safely. If you want a deeper side-by-side breakdown of both medicines before deciding, our Wegovy vs Mounjaro comparison sets out how the two drugs differ across efficacy, titration and tolerability in full detail.
A note on Ozempic: the mounjaro-to-ozempic conversion question
Ozempic is also semaglutide, but it is licensed in the UK for type 2 diabetes management, not for weight loss. The NHS and MHRA are clear on this distinction. Ozempic contains the same active molecule as Wegovy, but at different licensed doses (0.5mg and 1mg for diabetes), and prescribing it for weight loss would be off-label. Queries about an Ozempic to Mounjaro conversion chart are worth addressing directly: if weight management is your goal, the relevant comparison is between Mounjaro and Wegovy, not Ozempic.
Similarly, Rybelsus is oral semaglutide licensed for type 2 diabetes at 3mg, 7mg and 14mg doses. Those tablet strengths are not the same product as Wegovy tablets (which use a different dose schedule: 1.5mg → 4mg → 9mg → 25mg). Never substitute one for the other, and never seek Ozempic or Rybelsus as a route to weight-loss treatment.
Which of the licensed weight-loss medicines suits you (Wegovy injection, Wegovy tablet, or Mounjaro) is a clinical decision that a prescriber makes with you, based on your health history, your current medication, and your goals. Our clinical team at the prescriber level reviews every consultation the same day. If you are ready to explore your options, start your free consultation and a prescriber will assess the right starting point for you.
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