Moving from 2.4mg Wegovy to Mounjaro: what the clinical evidence says

The SURMOUNT-5 head-to-head: why 2.4mg Wegovy is the comparison point that matters

SURMOUNT-5 is the trial that makes this question answerable. Published in the New England Journal of Medicine in 2025, it randomised 751 adults with obesity but without type 2 diabetes to either tirzepatide (Mounjaro) or semaglutide 2.4mg (Wegovy) for 72 weeks. Participants on tirzepatide lost a meaningfully greater proportion of body weight on average. If you want to understand how 2.4mg Wegovy compares specifically against 10mg Mounjaro, the dose-level breakdown sheds useful light on where the difference becomes most pronounced. The comparison used the 2.4mg dose of semaglutide specifically because that was, until recently, the licensed maintenance ceiling for Wegovy, making it the direct benchmark against which Mounjaro competes.

SURMOUNT-1, separately, found that tirzepatide at its highest dose produced average body-weight reductions of around 20–21% over 72 weeks. STEP 1, the equivalent trial for how Wegovy compares overall, reported around 15% average loss at semaglutide 2.4mg over 68 weeks. Neither figure is a guarantee for any individual; both are average results from controlled trials, and real-world outcomes vary. The NICE technology appraisal of tirzepatide (TA1026) acknowledged indirect comparisons favouring tirzepatide when it recommended Mounjaro for eligible adults in England from December 2024.

One important caveat: Novo Nordisk has since received MHRA approval for a 7.2mg Wegovy dose, which narrows the gap. If you are reviewing this switch because you feel 2.4mg has stalled, it is worth discussing the 7.2mg option with a prescriber before assuming a switch is the only route forward.

How the two medicines actually differ, and what that means for someone already on 2.4mg semaglutide

Wegovy acts on a single gut-hormone receptor: GLP-1. Mounjaro activates both GLP-1 and GIP receptors simultaneously, which appears to amplify the appetite and metabolic effects beyond what GLP-1 stimulation alone achieves. That mechanistic difference is why the two medicines are not simply dose equivalents of each other, there is no 1:1 conversion figure endorsed in UK clinical guidance. For a fuller look at what moving from 2.4mg Wegovy to Mounjaro actually involves, including what to expect at each stage, it is worth reading through the detail before your prescriber appointment.

For someone who has been stable at 2.4mg Wegovy, switching to Mounjaro means restarting a titration schedule, beginning at 2.5mg regardless of where they were on semaglutide. That is not a downgrade; the 2.5mg tirzepatide pen is a tolerability step designed to let your system adjust to the new mechanism. The question of dose conversion between the two medicines does not have a simple numerical answer, and prescribers approach it case by case rather than by formula.

Practically speaking, both are once-weekly subcutaneous injections, pre-filled pens, refrigerated storage. Someone comfortable with the Wegovy pen will find the Mounjaro KwikPen a familiar format. When your order arrives, the DPD tracking notification comes through the morning of delivery; the pen itself arrives in plain packaging with no branding visible on the outside.

Side-effect profile comparison and what to expect when switching

The gastrointestinal side-effect profile of both medicines overlaps substantially, nausea, loose stools, constipation, reflux and fatigue feature in both, most prominently at initiation or after a dose increase. Restarting the titration ladder on Mounjaro after a period on Wegovy means that early-dose GI effects can recur even if you had grown tolerant of semaglutide. This is not a sign that the medicine is unsuitable; it typically settles within a few weeks as the body adjusts.

The NHS patient information on tirzepatide sets out the full side-effect list alongside the signs that require prompt medical attention, including severe or persistent abdominal pain that radiates to the back, which warrants urgent assessment. Both medicines carry a Black Triangle (▼) designation with the MHRA, meaning they are subject to additional monitoring; patients can report suspected side effects via the Yellow Card scheme. For women using oral contraceptives, tirzepatide specifically requires adding a barrier method for the first four weeks of treatment and for four weeks after each dose increase, because it may reduce pill absorption, semaglutide carries no equivalent caution in current UK guidance.

Pregnancy and breastfeeding are contraindications for both medicines. Neither is licensed for under-18s.

A factual comparison: 2.4mg Wegovy vs Mounjaro at a glance

Trial averages are population figures, not individual predictions. The cost difference between the two treatments is another factor worth reviewing before a decision is made. Many people also find it helpful to read about which Mounjaro dose is considered equivalent to 2.4mg Wegovy when weighing up their options. Which medicine is right for you depends on your health history, current response to treatment and your prescriber's assessment, explore your options at our weight-loss treatment page, or read more about how these treatments fit into a broader weight-management plan. Our clinical team is described on the prescriber profile page if you want to know who reviews your consultation. Speak to our prescribers to work through which direction makes clinical sense for you.