Mounjaro®
Starting from £179.99/mo
Start journey Learn moreWhat the dosage switch actually looks like, step by step
Step 1: Understanding why the dose ladders don't map onto each other
Mounjaro's six-step schedule runs from 2.5 mg up to 15 mg, with each pen delivering four weekly injections. Wegovy's schedule runs from 0.25 mg through to 2.4 mg, and now extends to 7.2 mg following MHRA approval of the dedicated single-dose 7.2 mg pen in April 2026. The numbers look incomparable because the medicines are measured differently and act through different mechanisms, tirzepatide activates both GIP and GLP-1 receptors, while semaglutide targets GLP-1 alone. Neither number is intrinsically stronger than the other at face value.
That mechanistic difference matters for tolerability. Someone well-settled on 10 mg Mounjaro is not guaranteed to tolerate Wegovy 2.4 mg from week one; gastrointestinal side effects can resurface when switching, even if you handled titration smoothly the first time. A quick habit worth building: before each new pen, check the patient information leaflet that came in the box, it takes under a minute and flags anything you should watch for at that specific dose.
Our Mounjaro to Wegovy dose conversion guide goes deeper on how clinicians approach this mapping, but the short version is that there is no universal equivalence table the prescribing community has agreed on.
Step 2: What your prescriber actually considers before deciding a Wegovy starting dose
When a prescriber reviews a switch, they are weighing several factors at once. How long you have been on Mounjaro, which dose you have reached, how much weight you have lost, and why you are switching all feed into the decision. If you are trying to work out where you might land on Wegovy before your consultation, our page on switching from Mounjaro to Wegovy and what dose to expect walks through the key considerations in plain terms. Common reasons include supply disruption, a preference for the single-receptor approach, cost changes following Eli Lilly's September 2025 UK price adjustment, or tolerance issues with tirzepatide.
The NICE technology appraisal TA1026 for tirzepatide and the equivalent TA875 for semaglutide both set out eligibility criteria separately; meeting one does not automatically mean you meet the other, and the clinical pictures differ. A prescriber may choose to restart Wegovy at a cautious dose (0.25 mg or 0.5 mg) to test tolerability, even if you are switching from a high Mounjaro dose, rather than assuming equivalence.
If you are thinking about switching from Wegovy to Mounjaro instead, the same logic applies in reverse. Our guide to switching from Wegovy 2.4 mg to Mounjaro covers that direction in detail.
Step 3: The switch in practice, what the comparison looks like on paper
The table below summarises the two medicines' licensed dose structures side by side. Numbers are drawn from the respective product information and NICE appraisals; they describe the medicines' schedules, not what any individual should take.
| Feature | Mounjaro (tirzepatide) | Wegovy (semaglutide injection) |
|---|---|---|
| Mechanism | Dual GIP and GLP-1 receptor agonist | GLP-1 receptor agonist |
| Starting dose | 2.5 mg once weekly | 0.25 mg once weekly |
| Maximum licensed dose | 15 mg once weekly | 7.2 mg once weekly (from April 2026) |
| Typical titration interval | ~4 weeks per step (prescriber-directed) | ~4 weeks per step (prescriber-directed) |
| Average weight loss (clinical trials) | ~20–21% at 15 mg (SURMOUNT-1, 72 weeks) [NEJM] | ~15% at 2.4 mg (STEP 1, 68 weeks) [NEJM] |
| NICE recommendation | TA1026: BMI ≥35 + ≥1 comorbidity (thresholds lower for some ethnic backgrounds) | TA875: BMI ≥35 + ≥1 comorbidity, specialist service, max 2 years |
In the SURMOUNT-5 head-to-head trial (published in the New England Journal of Medicine, 2025), tirzepatide produced greater average weight reduction than semaglutide 2.4 mg over 72 weeks in adults with obesity but without diabetes. The new 7.2 mg Wegovy dose narrows that gap in early data. Neither figure predicts your individual response.
Which medicine is right after a switch: what our prescribers look at
A switch is not always straightforward, and the direction matters. Moving from a high Mounjaro dose to Wegovy, or converting between these medicines at a given dose level, each carries its own considerations. Prescribers also look at whether the reason for switching is likely to recur, if Mounjaro supply was the problem, the same issue could arise again.
People asking about switching from 7.5 mg Mounjaro to Wegovy or from 10 mg Mounjaro to Wegovy often expect a like-for-like equivalent. There isn't one. What there is, is a prescriber willing to take your full history seriously and propose a starting dose that prioritises safety over speed.
Both medicines share a GI-led side-effect profile (nausea, changes in bowel habit, reduced appetite) and both are prescription-only. Neither is suitable during pregnancy, breastfeeding, or when trying to conceive; they are not licensed for under-18s. If you are on oral contraceptives and switching to tirzepatide, you need to add a non-oral method for the first four weeks of treatment and for four weeks after each dose increase, as NHS England guidance explains. No equivalent absorption concern has been identified for semaglutide.
Which medicine suits you after a switch is a clinical decision our prescribers make with you, not something a comparison table can settle. Speak to our prescribers through a free consultation and get a decision based on your actual situation, not a generalised dose chart.
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