Mounjaro®
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Start journey Learn moreHow a Wegovy-to-Mounjaro switch is assessed in practice
You're mid-treatment on Wegovy 1.7mg, here's the situation
Wegovy (semaglutide) 1.7mg is the fourth rung of a five-step titration schedule that runs from 0.25mg up to the 2.4mg maintenance dose. If you're at 1.7mg, you're close to the top of the Wegovy ladder but not yet at full maintenance. Perhaps weight loss has slowed, perhaps you're considering switching before reaching 2.4mg, or perhaps your prescriber has raised the question of trying a different mechanism.
Mounjaro (tirzepatide) works differently. It activates both the GIP and GLP-1 receptors (two distinct appetite and blood-sugar pathways) where Wegovy acts on GLP-1 alone. That dual mechanism is why the semaglutide-to-tirzepatide conversion isn't a straight milligram-for-milligram translation. The starting doses aren't equivalent; the tolerability ramp is its own thing.
In SURMOUNT-5, a 72-week head-to-head trial published in the New England Journal of Medicine in 2025, tirzepatide produced greater average weight reduction than semaglutide 2.4mg in adults with obesity who did not have diabetes. That context matters when you're thinking about whether a switch might offer more. The specific question of what dose applies at 1.7mg turns on clinical judgement rather than a formula.
What does the dose comparison actually look like?
The table below sets out the two titration schedules side by side. The doses aren't equivalent step-for-step, the schedules overlap at different points in each treatment journey. Refer to the NHS patient information on tirzepatide and the equivalent NHS page on semaglutide for the full clinical picture on each medicine.
| Wegovy (semaglutide) weekly dose | Typical step in schedule | Broadly comparable Mounjaro (tirzepatide) starting consideration |
|---|---|---|
| 0.25mg | Step 1 (starter) | 2.5mg (starter dose (tolerability, not therapeutic) |
| 0.5mg | Step 2 | 2.5mg–5mg (prescriber-dependent) |
| 1.0mg | Step 3 | 5mg (prescriber-dependent) |
| 1.7mg | Step 4 | 5mg–7.5mg (no fixed equivalence; prescriber decides based on response and history) |
| 2.4mg | Step 5 (maintenance) | 7.5mg–10mg or higher (clinical assessment required) |
These ranges reflect how clinicians tend to approach the switch) not a fixed protocol. Mounjaro always starts at 2.5mg for patients new to tirzepatide, regardless of where they were on Wegovy, unless there's a documented clinical reason to start differently. A prescriber reviewing your transfer will look at your duration on each Wegovy dose, your weight trajectory and any side effects you've experienced. For a fuller read on how the 1.7mg Wegovy dose is considered alongside Mounjaro strengths, that page sets out the detail.
What changes (and what stays the same) after switching
Both medicines are once-weekly subcutaneous injections, so the injection routine itself is familiar. Storage is the same: refrigerated between 2°C and 8°C, with a limited room-temperature window set out in the Patient Information Leaflet. The side-effect profile is broadly similar too, nausea, constipation, indigestion and other gastrointestinal symptoms are common to both, typically most noticeable in the first few weeks at a new dose. They usually settle.
What shifts is the receptor mechanism and, for many people, the efficacy ceiling. Mounjaro's dual-agonist action can produce a different appetite-suppression pattern. Some patients find the GI adjustment when switching feels similar to starting a new medicine from scratch, which is essentially what it is. That's worth knowing before you make the call, ideally before 12pm on a weekday so any approved prescription can be dispatched the same day.
If you're weighing up the cost side, a breakdown of what Wegovy and Mounjaro cost in the UK covers what the prices include, and what they often don't. The direct side-by-side at 1.7mg is also worth reading before your consultation.
The clinical decision: why a prescriber needs to review this with you
Switching GLP-1 medicines mid-treatment isn't automatic. NICE's appraisal of tirzepatide (TA1026) and the corresponding guidance for semaglutide set eligibility criteria, and a prescriber needs to be satisfied that Mounjaro is appropriate for you specifically, your BMI, your comorbidities, your current progress and your medical history all come into the picture. Transfer patients at nume provide evidence of their current treatment; that's the clinical review in action.
There's no approved head-to-head dose-equivalence table in UK prescribing guidance. The reverse switch from Mounjaro to Wegovy carries the same caveat. What exists is clinical judgement applied to your individual situation. Our prescribers work through that with you during the consultation. Which medicine suits you, and at what dose, is a clinical decision made with you, not one a conversion chart can make for you. Check your eligibility with our prescribers if you'd like that conversation.
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