Wegovy 0.5mg and Its Mounjaro Equivalent: What the Doses Actually Mean

The misconception: that doses of two different medicines can be swapped like-for-like

The phrase "0.5mg Wegovy equivalent to Mounjaro" implies a clean translation exists, that you can find the Mounjaro pen that sits at exactly the same point. That is not how these medicines work. Wegovy (semaglutide) is a GLP-1 receptor agonist. Mounjaro (tirzepatide) activates both the GIP and GLP-1 receptors simultaneously, a fundamentally different pharmacological action, and the only dual-agonist weight-loss medicine currently licensed in the UK. Their dose ranges do not overlap in milligrams: Wegovy runs from 0.25mg up to 2.4mg per week (or 7.2mg with the newer higher-dose pen), while Mounjaro runs from 2.5mg to 15mg. The numbers sit in entirely different ranges because the molecules bind differently and require different quantities to produce their effects. Comparing them by milligram is a bit like comparing paracetamol 500mg to ibuprofen 200mg and concluding one is stronger because the number is bigger. The figures are not the same currency. For a broader look at how these two medicines sit against each other overall, the Wegovy vs Mounjaro comparison page covers the full picture.

Where 0.5mg sits in Wegovy's schedule, and what that means practically

Wegovy's titration runs in roughly four-week steps: 0.25mg, then 0.5mg, then 1.0mg, 1.7mg, and finally 2.4mg as the standard maintenance dose (with 7.2mg now approved for eligible patients who need it). The 0.5mg dose is the second rung, a step up from the introductory dose, still within the early tolerance-building phase of treatment, not yet at a therapeutic maintenance level. Most people are at 0.5mg only transiently, for around four weeks, before their prescriber moves them to 1.0mg. Asking what Mounjaro dose equates to 0.5mg Wegovy therefore roughly asks: what is Mounjaro's early-treatment equivalent? Mounjaro begins at 2.5mg, which serves the same purpose, settling the body into the medicine before the dose is increased toward the range where meaningful weight loss tends to occur. Both 0.5mg Wegovy and 2.5mg Mounjaro are transition doses, not endpoints. That structural parallel is probably the most honest answer to what 0.5mg Wegovy corresponds to on Mounjaro's schedule, and it comes with the caveat that a prescriber, not a comparison chart, decides the actual starting point. The clinical context for this dose equivalence question matters more than any number.

What trial evidence says about the medicines at comparable stages

The SURMOUNT-5 trial (the only head-to-head, published in the New England Journal of Medicine in 2025) compared tirzepatide against semaglutide 2.4mg over 72 weeks in adults with obesity and no diabetes. Tirzepatide produced greater average weight reduction across the trial period. SURMOUNT-1 (72 weeks, tirzepatide at 15mg) showed approximately 20–21% average body-weight reduction. The STEP 1 trial of semaglutide 2.4mg reported roughly 15% average reduction over 68 weeks, as summarised by NICE's appraisal of Wegovy (TA875). Neither of those figures represents an early-dose result, they represent what happened at the highest doses over the full trial. Comparing the two medicines at 0.5mg Wegovy and 2.5mg Mounjaro specifically is not something published trial data addresses directly, because those are starting doses, not the doses the trials were powered to measure. If you are switching between the two medicines, or wondering which to start, the guide to switching between Mounjaro and Wegovy explains what prescribers consider, and how 1mg Wegovy compares to Mounjaro covers the next step in the semaglutide schedule.

How a prescriber actually decides which medicine and dose to start

Eligibility for both medicines in a private setting requires a BMI of 30 or above, or 27 or above with at least one weight-related condition such as high blood pressure, type 2 diabetes, or obstructive sleep apnoea, though BMI alone is not the whole assessment. A prescriber also considers your medical history, any medicines you already take, your tolerance of GI side effects in the past, and your preferences around injection vs. tablets. Price context is relevant too: how Mounjaro and Wegovy compare on cost is a practical factor many patients raise. At higher doses, tirzepatide's evidence base currently shows greater average weight loss; at the dose equivalent of early treatment, the gap is less well-characterised. Which suits you is a clinical decision our prescribers make with you, based on your full picture, not a milligram comparison. Our clinical team, including our lead prescriber, reviews every consultation the same day it is submitted. If you are ready to explore your options, check your eligibility and start your free consultation.