Should You Switch to Wegovy? What the Evidence Says

What the trial data actually shows about Wegovy's weight-loss results

The clinical case for Wegovy starts with STEP 1, published in the New England Journal of Medicine. Over 68 weeks, adults treated with semaglutide 2.4mg lost an average of around 15% of their body weight alongside lifestyle changes. That was a landmark figure at the time of approval. In 2026, the picture shifted further: the MHRA approved a 7.2mg maintenance dose, and the dedicated single-dose 7.2mg pen followed in April 2026. Trials of that higher dose reported average weight reduction of around 20.7% over 72 weeks, narrowing the gap with tirzepatide (Mounjaro) considerably.

The SURMOUNT-5 head-to-head trial, published in 2025, compared tirzepatide directly with semaglutide 2.4mg in adults with obesity but without diabetes. Tirzepatide produced a greater average weight reduction over 72 weeks. That said, individual responses vary considerably, and a medicine that works better on average across a trial population does not automatically work better for a specific person. The NICE appraisal of semaglutide (TA875) and the parallel appraisal of tirzepatide both reflect this, NICE recommends each on distinct eligibility criteria, and the committee noted that indirect comparisons favour tirzepatide while acknowledging that both medicines produce clinically meaningful weight loss.

The reason many people ask about switching is straightforward: they started on one medicine and either found it hard to tolerate, hit a plateau, or read about newer options. All of those are legitimate starting points for a clinical conversation, and our guide to switching to Wegovy sets out what that process typically involves.

Mounjaro vs Wegovy: a factual side-by-side

A question our prescribers hear most weeks is some version of: "I've been on Wegovy for a few months, should I be on Mounjaro instead?" There is no universal right answer, but the factual differences below inform the conversation.

Figures from NICE TA1026 (tirzepatide recommendations) and NICE TA875; trial averages from SURMOUNT-1 and STEP 1. Individual results differ. Two things worth flagging: Ozempic is also semaglutide, but it is licensed for type 2 diabetes, not weight management, if you want to read more about how semaglutide products differ, the Wegovy vs Ozempic page covers that clearly. And Rybelsus (oral semaglutide) is similarly a diabetes medicine, not a weight-loss treatment.

Who might benefit from switching, and who probably wouldn't

Switching makes the most clinical sense when there is a specific reason: inadequate response on the current medicine at the highest tolerated dose, side effects that have not settled, a change in health conditions that affects eligibility, or a preference for a different administration route (the Wegovy overview covers the injection and the new tablet option). It makes less sense as a reflexive chase for the newest product if the current one is working well and being tolerated.

Coming from Saxenda (liraglutide)? The switch process differs from a Mounjaro-to-Wegovy move; our page on switching from Saxenda to Wegovy sets out the clinical picture. If you are currently on Ozempic and wondering about the route to a weight-management licence, can you switch from Ozempic to Wegovy explains the licensing distinction. People moving in the other direction can find similar detail on switching from Wegovy to semaglutide.

Eligibility for both Wegovy and Mounjaro through a private route generally 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, high cholesterol or obstructive sleep apnoea. Lower thresholds apply for some ethnic backgrounds under UK guidance. A BMI figure alone does not tell the whole story, the prescriber weighs up your full medical history, any medicines you take, and whether a switch is clinically appropriate right now.

The NHS England guidance on weight management injections also notes that women using oral contraceptives who start tirzepatide should add a barrier method for four weeks after each dose increase, because tirzepatide may reduce pill absorption. No equivalent evidence exists for semaglutide. Worth knowing before you switch direction.

How to actually make the switch through a regulated pharmacy

Any switch between GLP-1 medicines is a prescribing decision, not a shopping choice. Genuine supply matters too: the MHRA has warned repeatedly about fake weight-loss pens sold online, with some containing insulin rather than the labelled medicine. Verifying a pharmacy on the GPhC register before ordering any prescription treatment is the single most useful safety check you can do. Sellers offering these medicines without a prescription, via social media or at prices well below the private market are the clearest red flags.

At nume, every switch request is treated as a fresh clinical review. Our prescribers check your current dose, how long you have been on it, any side effects, and your goals before recommending any change. You can explore all available licensed treatments on our weight-loss treatments page, or look at the broader picture on the weight loss overview. Which medicine suits you is a clinical decision our prescribers make with you, the consultation is where that conversation starts. There is no guesswork, and no algorithm making the call.