What Is the Wegovy Equivalent to Mounjaro 12.5 mg?

Why can't you just map Mounjaro 12.5 mg straight onto a Wegovy dose?

Mounjaro (tirzepatide) activates both the GIP and GLP-1 receptors, while Wegovy (semaglutide) targets GLP-1 alone. That difference in mechanism means the two medicines don't share a common scale, and milligrams of one don't translate to milligrams of the other in any pharmacologically meaningful way. Mounjaro runs a six-step ladder from 2.5 mg up to 15 mg, and the starting 2.5 mg Mounjaro dose already sits in an interesting position relative to Wegovy; Wegovy climbs from 0.25 mg through to 2.4 mg as its standard maintenance dose, and now up to 7.2 mg following MHRA approval of the dedicated 7.2 mg single-dose pen in April 2026. Comparing them by dose number is like comparing shoe sizes across two different sizing systems, the numbers mean different things.

At 12.5 mg, a patient is one step below Mounjaro's ceiling. They've typically been on treatment for at least five months, tolerating progressive titration. Asking what "the equivalent" is in Wegovy terms usually means: what Wegovy dose produces a comparable degree of weight reduction? That's a question the trial data can partially answer, but it's not the same as a clinical switching recommendation. If you're thinking about moving from Mounjaro 12.5 mg to Wegovy specifically, that requires a prescriber conversation, not a dose table.

What does the evidence say about results at this stage of treatment?

The clearest direct comparison comes from SURMOUNT-5, a 72-week head-to-head trial in adults with obesity and no diabetes, published in the New England Journal of Medicine. Tirzepatide produced greater average weight loss than semaglutide 2.4 mg across the trial period. SURMOUNT-1 separately reported around 20–21% average body-weight reduction at the 15 mg dose; results at 12.5 mg sit somewhat below that ceiling. Semaglutide 2.4 mg, in the STEP 1 trial, produced around 15% average weight loss at 68 weeks.

The table below puts the key figures side by side, drawing on those trial results and NICE's appraisal of tirzepatide (TA1026), which noted that indirect comparisons favour tirzepatide. These are population averages from clinical trial conditions, not predictions for any individual.

Worth noting: the newer 7.2 mg Wegovy dose reported around 20.7% average weight loss over 72 weeks in trials, which narrows the gap with tirzepatide considerably. So the comparison between these two medicines is moving, and your prescriber will work from current evidence, not a static snapshot.

Does being on 12.5 mg Mounjaro affect which Wegovy dose you'd start on if you switched?

This is the practical version of the equivalence question, and it's one our prescribers at our clinical team handle regularly. The short answer: prior exposure to tirzepatide doesn't mean you skip to a matching Wegovy dose. Semaglutide's titration schedule is its own clinical protocol; a prescriber assesses your history, tolerance record and current weight trajectory before deciding where on that ladder to begin. Jumping straight to 2.4 mg (the closest in outcome terms to 12.5 mg tirzepatide) without proper titration is not standard practice and carries a higher side-effect burden.

The starting point also depends on why you're considering switching. Supply issues, tolerability, clinical response, or simply wanting the tablet form of semaglutide (the Wegovy pill was approved by the MHRA in June 2026) are all different scenarios with different clinical answers. Check your current pen's dose setting before any conversation with a prescriber, it takes seconds and means you're giving them accurate information from the start. A broader view of how the two medicines compare across the full picture is covered on our Wegovy vs Mounjaro comparison page.

Which one is the right choice at this stage of a weight-loss journey?

Honestly, that's not a question this page can answer, and any page that claims otherwise should be treated with scepticism. By the time someone is asking about 12.5 mg equivalence, they've usually been on treatment long enough to have real data: how much weight they've lost, how they've tolerated each dose increase, whether they've hit a plateau. That information shapes the clinical answer far more than any trial average. If tirzepatide is working well at 12.5 mg, continuing to 15 mg may be the more straightforward path. If tolerability is the issue, or supply has interrupted treatment, switching needs a proper clinical assessment, not a conversion formula.

The dose conversion question comes up often enough that it's worth being clear: there is no officially validated conversion chart between these two medicines, and even a relatively low Wegovy dose like 1 mg sits in a complicated position when you try to map it against Mounjaro. Prescribers use clinical judgement informed by individual history, which is exactly what the consultation process at nume is built around. For a cost-based angle on choosing between the two, the price comparison page covers what both typically cost through private services. Which suits you is a clinical decision our prescribers make with you.