Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow the two dose ladders compare — and what the trials tell us about equivalent effect
Step 1: Understanding that the ladders don't line up
Semaglutide (Wegovy) and tirzepatide (Mounjaro) are titrated in completely separate steps. Wegovy starts at 0.25 mg weekly and climbs through 0.5 mg, 1.0 mg and 1.7 mg to a standard maintenance dose of 2.4 mg; the MHRA approved a higher 7.2 mg dose in January 2026, with a dedicated single-dose pen confirmed on 14 April 2026. Mounjaro starts at 2.5 mg (a tolerability period rather than a therapeutic target) and steps through 5 mg, 7.5 mg, 10 mg, 12.5 mg to a maximum of 15 mg.
The numbers look very different in milligrams, but milligrams alone tell you nothing useful here. These are entirely distinct molecules acting on different receptors: semaglutide activates GLP-1 receptors only, while tirzepatide activates both GLP-1 and GIP receptors. That dual action is the reason the doses are not interchangeable and why prescribers don't apply a conversion formula when someone switches. You can read more about what a clinical switch between the two actually involves.
Dose decisions are always made by the prescriber based on what you've tolerated, what you've achieved, and your overall health picture.
Step 2: What the trial data shows about comparable effectiveness
The closest thing to an equivalent-dose comparison in the published literature comes from the SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025. This was a direct head-to-head study in 751 adults with obesity and no diabetes, running over 72 weeks. Participants received either tirzepatide at the highest tolerated dose or semaglutide 2.4 mg weekly. Tirzepatide produced greater average weight reduction, making it the first randomised trial to confirm the superiority signal that indirect comparisons from earlier studies had suggested.
For context, SURMOUNT-1 (semaglutide's counterpart, STEP 1, ran 68 weeks) showed roughly 15% average body-weight reduction on semaglutide 2.4 mg, while tirzepatide at 15 mg produced around 20–21% average reduction in SURMOUNT-1. Those figures come from separate trials with separate populations, so a direct percentage comparison carries caveats, but they are the numbers NICE used when evaluating both medicines.
NICE recommended tirzepatide in Technology Appraisal TA1026, published December 2024, partly on the strength of its relative performance. The appraisal committee noted that indirect comparisons favour tirzepatide, a finding then reinforced by SURMOUNT-5. If you are weighing the two medicines on results, our Wegovy vs Mounjaro comparison covers the evidence in more detail.
Step 3: Reading the comparison table, doses, pathways and key facts
The table below lays out what is known factually about each medicine at the dose levels most relevant to a switching or selection decision. The 7.2 mg semaglutide row reflects the newer data; early trial results at that dose reported roughly 20.7% average weight loss over 72 weeks, approaching the tirzepatide 15 mg figures. That gap-narrowing is clinically significant and forms part of the conversation our prescribers have with patients considering Wegovy today.
| Feature | Semaglutide (Wegovy) 2.4 mg | Semaglutide (Wegovy) 7.2 mg | Tirzepatide (Mounjaro) 15 mg |
|---|---|---|---|
| Receptor target | GLP-1 only | GLP-1 only | GLP-1 + GIP (dual) |
| Average weight loss in trials | ~15% over 68 weeks [STEP 1, NEJM] | ~20.7% over 72 weeks [Novo Nordisk data] | ~20–21% over 72 weeks [SURMOUNT-1, NEJM] |
| UK licence status (weight management) | Licensed; NICE TA875 | Licensed (MHRA, April 2026) | Licensed; NICE TA1026 |
| Dosing frequency | Once weekly injection | Once weekly injection | Once weekly injection |
| Standard titration steps | 0.25 → 0.5 → 1.0 → 1.7 → 2.4 mg | Continues beyond 2.4 mg to 7.2 mg | 2.5 → 5 → 7.5 → 10 → 12.5 → 15 mg |
| Oral contraceptive interaction | No equivalent NHS warning issued | No equivalent NHS warning issued | Add non-oral contraception for 4 wks from each dose increase |
Sources: STEP 1, NEJM; SURMOUNT-1, NEJM; MHRA 7.2 mg approval, GOV.UK.
Step 4: What this means if you are switching or choosing for the first time
If you are moving from semaglutide to tirzepatide, the prescriber will not simply match your current milligram dose to a "tirzepatide equivalent." Instead, they typically start you at Mounjaro's 2.5 mg pen and titrate from there, adjusting to what you tolerate and how your body responds. The same applies in reverse. Our page on switching from Mounjaro to Wegovy explains that direction in full.
If you are choosing between the two for the first time, the prescriber will weigh your BMI, any existing conditions, your contraception arrangements (particularly relevant for tirzepatide, see the table above), your preferences about injection experience, and cost. A useful place to ground that conversation is our cost comparison for Wegovy and Mounjaro, which sets out what each medicine typically costs privately in the UK.
One practical note: if you are thinking about starting treatment around a bank holiday or payday and wondering whether timing affects supply, it genuinely can, orders placed before 12pm on a working day are dispatched the same day, so planning a day ahead of any holiday period helps. The clinical review process itself takes the same day regardless of when you order.
Our clinical team reviews every consultation personally. Which medicine suits you, and at what starting dose, is a clinical decision made with our prescribers, not an algorithm, and not something a milligram table can settle alone. Patients switching at 1 mg semaglutide will find a dedicated guide covering how that particular crossover point is approached, and those finishing the Wegovy ladder can read about moving across from the 2.4 mg maintenance dose. If you would like to explore your options, you can start your free consultation today.
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