0.25mg Wegovy Compared to Mounjaro at the Same Early Stage

You've just been told you could try either, here's what you're actually choosing between

Wegovy and Mounjaro both come up in the same conversation because both are licensed in the UK for weight management in adults, and both work by influencing appetite hormones. But they do so differently. Wegovy contains semaglutide, a GLP-1 receptor agonist; Mounjaro contains tirzepatide, which activates two receptors, GIP and GLP-1. That dual action is the practical distinction most people want to understand before picking one.

At the starter stage, 0.25mg Wegovy and 2.5mg Mounjaro are both tolerability doses. Neither is expected to drive meaningful weight loss in week one. Their job is to let your digestive system adjust before the dose increases. The titration schedules then diverge: Wegovy climbs through 0.5mg, where its profile against Mounjaro shifts noticeably, then 1.0mg, 1.7mg and up to 2.4mg over roughly five months; Mounjaro moves through 5mg, 7.5mg, 10mg, 12.5mg and up to 15mg over a similar period, with a prescriber guiding each step. For a fuller look at how the dose ladders compare side by side, this breakdown of the full Wegovy dose compared to Mounjaro maps each rung in detail.

The route to the maintenance dose matters because most of the trial evidence is based on participants reaching and staying at the highest tolerated dose. Comparing the two medicines purely at starter stage tells you about tolerability profiles, not long-term results.

What the head-to-head trial found (and what it didn't measure

The SURMOUNT-5 trial) published in the New England Journal of Medicine in 2025, was the first large-scale, randomised head-to-head study comparing tirzepatide directly against semaglutide 2.4mg in adults with obesity and without type 2 diabetes. Over 72 weeks, tirzepatide produced greater average weight reduction. NICE's appraisal of tirzepatide (NICE TA1026) notes that indirect comparisons also favour tirzepatide, though it acknowledges the evidence base for direct comparison was limited at the time of the original review.

That said, SURMOUNT-5 compared tirzepatide against the 2.4mg maintenance dose of Wegovy, not the newer 7.2mg pen, approved by the MHRA in April 2026 for adults with a BMI of 30 or above. Early data on the 7.2mg dose reports around 20.7% average weight loss over 72 weeks, which narrows the gap considerably.

None of this is measured at 0.25mg. If you are weighing up how 0.25mg Wegovy compares to Mounjaro at the equivalent starter stage, the starting dose comparison you searched for is really asking about two things: which medicine you're a candidate for, and which one your prescriber thinks fits your history, current medicines and health picture. For context on how the two stack up across the full dose range, our Wegovy vs Mounjaro page covers the wider evidence in one place.

The side-effect picture at the starter dose, and what tends to settle

A question our prescribers hear most weeks is whether one medicine has a gentler start than the other. Honestly, both share a GI-led side-effect profile at first: nausea, loose stools, constipation, indigestion and occasional fatigue are the most common early reports for both. The NHS tirzepatide page and the NHS semaglutide page list these in plain language for each.

For most people, these effects are most noticeable in the first week or two after starting or after a dose increase, then ease. Neither medicine is entirely free of this early adjustment period, which is precisely why both have a 0.25mg or 2.5mg introduction before anything higher. If you're switching from one to the other, or increasing your dose, keep your prescriber in the loop, the PIL and SmPC are the authoritative references for what to watch for. You can also read about how 1mg Wegovy compares to Mounjaro if you want to understand what changes as the dose steps up.

On contraception, there is one difference worth flagging. Women taking oral contraceptives should use an additional non-oral method for the first four weeks of Mounjaro and for four weeks after each dose increase, because tirzepatide's effect on gastric emptying may reduce pill absorption. NHS guidance does not highlight the same concern for semaglutide. Check the frequently asked questions section or raise it directly with our team.

Which one you can access, and how cost fits into the decision

Both medicines need a prescription following clinical assessment. Neither is available to simply order. Legitimacy matters here: the MHRA has warned repeatedly about counterfeit weight-loss pens sold online, including fake tirzepatide pens seized in the UK in 2025. Buying from a pharmacy you can verify on the GPhC register is the baseline check, nume's GPhC premises registration number is 9012878 if you want to look us up directly.

On cost, the two medicines now sit in different price brackets following Eli Lilly's list-price increase in September 2025, with Mounjaro's higher-dose pens rising sharply. If cost is a material part of your decision, a direct cost comparison between the two breaks down what the market looks like. At nume, one price covers everything: consultation, prescription, the treatment and delivery, you can find current treatment pricing on the treatment page.

Which medicine suits you is a clinical decision our prescribers make with you, not one a comparison table can settle on its own. Speak to our prescribers to get a personalised assessment.