0.25mg Wegovy Compared to Mounjaro: What the Starting Dose Decision Actually Involves

Why comparing a 0.25mg Wegovy dose to Mounjaro's 2.5mg starter is only part of the picture

Both Wegovy (semaglutide) and Mounjaro (tirzepatide) use a stepped titration approach because the medicines work on the gut and appetite in ways the body needs time to adjust to. The full Wegovy vs Mounjaro comparison covers the two medicines across their entire dose ranges, but if you're specifically at the starting-dose stage, the most useful thing to understand is this: 0.25mg semaglutide and 2.5mg tirzepatide both serve the same purpose. They're there to reduce nausea and other gastrointestinal side effects in the first four weeks, not to deliver the medicine's full clinical effect. Expecting significant weight change at either starting dose would be setting the wrong benchmark.

Wegovy's licensed titration in the UK runs from 0.25mg up through 0.5mg, 1.0mg, 1.7mg to a standard maintenance dose of 2.4mg weekly, with a higher 7.2mg dose now also approved by the MHRA for adults with a BMI of 30 or above. Mounjaro moves from 2.5mg through 5mg, 7.5mg, 10mg, 12.5mg to a maximum of 15mg. Titration timing in both cases is set by your prescriber, typically at roughly four-week intervals. If you want to understand how the first step up feels relative to Mounjaro, the guide comparing 0.5mg Wegovy to Mounjaro is worth reading alongside the guide on Wegovy doses compared to Mounjaro, which maps the schedules side by side.

Wegovy is a GLP-1 receptor agonist; Mounjaro acts on both the GIP and GLP-1 receptors, making it the only dual-agonist weight-loss medicine currently licensed in the UK. Whether that mechanistic difference matters for you specifically is something a prescriber will consider alongside your health history, not something a comparison article can settle.

What the trial evidence tells us, and what it can't

The clinical evidence base for both medicines is substantial. In the STEP 1 trial, semaglutide 2.4mg produced an average weight reduction of around 15% over 68 weeks, as reported in the New England Journal of Medicine. The SURMOUNT-1 trial showed tirzepatide at 15mg averaging around 20–21% body-weight reduction over 72 weeks. In the more recent SURMOUNT-5 head-to-head trial (72 weeks, adults with obesity, no diabetes), tirzepatide produced greater average weight loss than semaglutide 2.4mg; NICE's appraisal of tirzepatide (TA1026) acknowledges that indirect comparisons generally favour tirzepatide, while noting the clinical context matters enormously.

But those are maintenance-dose figures. If you're curious how the very first dose of Wegovy sits in that broader picture, the overview of 0.25mg Wegovy compared to Mounjaro explains what that initial stage does and does not tell you. Patients who respond well to one medicine don't always respond the same way to the other, and individual factors (medical history, how you tolerate gastrointestinal side effects, which receptor pathways your physiology responds to) shape outcomes in ways trial averages can't predict. The table below sets out the headline factual differences to help you structure that conversation with a prescriber.

If you're considering switching from one to the other, the question of dose conversion between Mounjaro and Wegovy doesn't follow a simple arithmetic rule, it's a clinical decision, not a calculation.

The practical factors that often tip the decision

Beyond the trial numbers, people choosing between these medicines often find the practical details matter just as much. Both require weekly subcutaneous injections; Mounjaro uses the KwikPen format, Wegovy uses a pre-filled auto-injector pen. Side-effect profiles are broadly similar, nausea, changes in bowel habit, and digestive discomfort are the most reported in both cases, generally most noticeable at the start of treatment or after a dose increase, and typically settling over the following weeks. The NHS patient information on semaglutide sets out the full side-effect picture for Wegovy, and a prescriber will go through the same information for Mounjaro at consultation.

Cost is another real-world consideration. Since Eli Lilly revised Mounjaro's UK list price in September 2025, private prices across providers have ranged roughly £149–£375 per month by dose. For a current view of what that looks like across providers, the Mounjaro vs Wegovy cost comparison sets out the picture honestly. A Monday order placed before 12pm (useful if, say, payday lands on a Friday and you're ready to start) means treatment dispatched that day if approved.

One thing worth knowing: women taking oral contraceptives starting Mounjaro should use an additional non-oral method for the first four weeks of treatment and for four weeks after each dose increase, because absorption of the pill may be reduced. The same concern hasn't been established for semaglutide. That single clinical detail has changed some patients' preferred choice, and it's the kind of factor that only surfaces in a proper prescriber conversation, not a comparison table. For the full eligibility picture on both medicines, the weight-loss treatment overview gives the licensed criteria clearly.

How our prescribers work through this decision with you

The right choice between Wegovy and Mounjaro at any dose, including the starting dose, depends on things a comparison page can't assess: your weight history, any conditions you're managing, medicines you're already taking, and your own preferences about how you'd like treatment to feel. Our clinical team reviews every consultation personally before anything is prescribed. If you have questions before starting, our FAQs cover many of the common ones, or you can reach the team directly via the contact page. The consultation is free, there's no subscription, and the treatment page shows current pricing clearly. Which medicine suits you is a clinical decision our prescribers make with you, not one a dose comparison alone can answer.