Moving from 1.7mg Wegovy to Mounjaro: how do the doses compare?

Why don't the dose numbers translate directly between Wegovy and Mounjaro?

Wegovy (semaglutide) is a GLP-1 receptor agonist. Mounjaro (tirzepatide) activates two receptors simultaneously (GLP-1 and GIP) making it the only dual-agonist weight-management medicine licensed in the UK. Because the pharmacological mechanisms differ, a 1.7mg dose of semaglutide cannot be mapped onto any specific tirzepatide strength by arithmetic alone. The drugs bind to different targets, at different receptor affinities, with different half-lives influencing how the body responds across the week.

Wegovy's dose ladder runs from 0.25mg up to 2.4mg, with 1.7mg sitting one step below the standard 2.4mg maintenance dose. Mounjaro's scale starts at 2.5mg (a tolerability step whose job is to let your system settle) and climbs through 5, 7.5, 10, 12.5 and 15mg. The numbers look larger, but they measure a different molecule in a different context. If you are wondering what 1.7mg of Wegovy is equal to in Mounjaro, it is worth understanding that comparing them directly would be like converting miles per hour into kilograms, because the units simply do not overlap. For further reading on how the two medicines' dose ladders relate, the Mounjaro-to-Wegovy dose conversion page walks through the structural differences in detail.

The NHS patient information page for tirzepatide and the equivalent NHS semaglutide page set out each medicine's approved schedule clearly, and are a useful reference if you want to read the official guidance before your consultation.

What does the clinical evidence say about how these two medicines compare at their effective doses?

The most reliable head-to-head data comes from SURMOUNT-5, a 72-week open-label trial published in the New England Journal of Medicine in 2025, which randomised 751 adults with obesity and no diabetes to tirzepatide or semaglutide 2.4mg. Tirzepatide produced greater average weight reduction across the dose range studied. Earlier individual trials had already shown meaningful results for each: SURMOUNT-1 reported around 20–21% average body-weight loss at 15mg tirzepatide, while STEP 1 reported approximately 15% average loss with semaglutide 2.4mg over 68 weeks, both versus placebo alongside lifestyle changes.

None of that data involves a 1.7mg maintenance dose of semaglutide specifically. The 1.7mg step in Wegovy's schedule is a titration stage, not a therapeutic endpoint, so published efficacy data at that exact dose is limited. If you are currently at 1.7mg, your prescriber will want to know why (whether you are mid-titration, whether side effects have slowed progression, or whether 1.7mg has become a settled long-term dose) before recommending any switch. For a fuller breakdown of how the two medicines compare at their licensed doses, see our Wegovy vs Mounjaro comparison.

A comparison of the headline evidence at licensed maintenance doses is set out below.

Numbers from clinical trials reflect group averages under trial conditions and do not predict any individual's result. Which medicine suits you depends on your health history, tolerability and what your prescriber finds at review.

What should someone at 1.7mg Wegovy expect if they switch to Mounjaro?

Switching between GLP-1-based medicines is not simply a matter of swapping pens on the next order day. A prescriber will typically want to see evidence that you are currently established on 1.7mg Wegovy, understand why you want to switch, and assess whether starting Mounjaro at 2.5mg is appropriate or whether a higher starting point is clinically justified given your prior treatment. Most switchers begin at 2.5mg regardless of where they were on semaglutide, to allow the body to adjust to a new molecule.

Timing matters practically too. If you are planning ahead around a holiday or a busy patch at work, flag that at consultation, a prescriber can help you plan the transition window sensibly rather than leaving a gap in treatment. Orders placed before 12pm on a working day ship the same day once approved, so a Monday consultation can have treatment with you by Tuesday.

The side-effect profile of tirzepatide overlaps significantly with semaglutide: nausea, loose stools, constipation, reflux and fatigue are the most commonly reported, generally most noticeable after starting or increasing a dose. Anyone who develops severe and persistent stomach pain, particularly if it radiates to the back, should seek urgent medical attention given the known association with acute pancreatitis across GLP-1 medicines. Our guide on what 1.7mg Wegovy is equivalent to in Mounjaro covers tolerability considerations for this specific switch point, and our detailed page on moving from 1.7mg Wegovy to Mounjaro explains the practical steps involved in making that change. For a cost comparison across the two medicines, Mounjaro vs Wegovy pricing in the UK sets out current private market context.

How does a nume prescriber approach a switch request like this?

At nume, every switch request is treated as a fresh clinical review. A GPhC-registered Independent Prescriber reads your consultation the same day, checking your current treatment evidence, your weight history, any conditions or medicines that bear on the decision, and whether the destination medicine is clinically suitable for you specifically. Transfer patients are asked to provide evidence of their current prescription; dose increases, including the step from 2.5mg upward on Mounjaro, require clinical sign-off before each one.

There is no algorithm making this call. That matters when a switch involves two medicines that are not directly comparable, because the decision draws on clinical judgement rather than a conversion table. If you would like to explore what a switch might look like for you, the weight-loss treatment overview explains both options, and you can read more about how we work on the about us page. Ultimately, which medicine is right for you is a clinical decision our prescribers make with you.