Switching from Semaglutide to Retatrutide: What the Evidence Actually Shows

The myth worth correcting first: retatrutide is not a licensed UK alternative you can switch to

A question our prescribers hear most weeks, in various forms, is whether retatrutide is available yet and whether someone on Wegovy could simply move across. The short answer is no, and not for any supply or cost reason, but because retatrutide has not been granted a UK marketing authorisation. The MHRA licenses medicines for specific indications once safety and efficacy data meet the required standard; retatrutide's phase 3 TRIUMPH programme is still running. Until that process concludes and a licence is granted, no UK pharmacy can legally supply it for weight management. Knowing this matters because some online content describes retatrutide in the present tense as though it were already available, which creates genuine confusion for people trying to make a practical decision about their treatment. If you have read a comparison framed as a live choice between the two, the framing is premature. If you are considering whether you can switch from semaglutide to retatrutide, our dedicated page explains exactly why that is not currently a viable option in the UK. For a deeper look at the specific differences in mechanism and evidence, our retatrutide versus semaglutide comparison covers that ground in full.

What the phase 2 trial data for retatrutide actually showed

Phase 2 results published in the New England Journal of Medicine reported that retatrutide at its highest tested dose produced average weight reductions of around 24% over 48 weeks in adults with obesity, figures that attracted significant attention in the clinical community. Semaglutide 2.4mg (Wegovy) produced around 15% average weight loss over 68 weeks in the STEP 1 trial, a finding underpinning NICE's recommendation of semaglutide (TA875). A direct numerical comparison is tempting, but the trials differ in duration, design, dose escalation schedules and participant profiles, so the numbers don't map cleanly onto each other. Phase 2 trials also enrol far fewer participants than phase 3 programmes, meaning the confidence intervals around those retatrutide figures are wide. The phase 3 TRIUMPH studies will either confirm those results at scale or revise them. The honest read is that early evidence is encouraging, and that it is also early. If you are already on semaglutide and wondering whether moving to retatrutide could be worthwhile, our guide to whether retatrutide is actually better than semaglutide explains what the evidence and the current regulatory position mean for that decision in practice.

A factual comparison of where each medicine stands today

The table above uses figures from the STEP 1 trial published in the New England Journal of Medicine for semaglutide and the phase 2 NEJM publication for retatrutide. Neither set of numbers is a guarantee of individual results.

What to do now if you're unhappy with your current semaglutide treatment

If you're on semaglutide and thinking about retatrutide because your results feel slow or the side effects have been difficult, the practical options available in the UK today are worth mapping out clearly. Tirzepatide (Mounjaro) is the only dual-agonist weight-loss medicine currently MHRA-licensed in the UK and the subject of a positive NICE appraisal (TA1026). The SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, found tirzepatide produced greater average weight reduction than semaglutide 2.4mg over 72 weeks, which makes it a clinically grounded alternative to discuss with a prescriber rather than a speculative future one. Separately, if your concern is the injectable route, the Wegovy tablet received MHRA approval in June 2026 as the UK's first licensed oral GLP-1 for weight management, and may suit people who prefer not to inject. If you moved from liraglutide before and are wondering how the dose adjustments work in practice, our page covering switching from liraglutide to semaglutide dosing explains the clinical rules that apply, which are worth understanding before you make any changes. Which medicine fits your situation is a clinical decision, not a chart comparison. Speak to our prescribers, they'll review your history and the evidence together with you, without a waiting list.