Switching to Wegovy after Mounjaro: the decision, the differences, the clinical picture

Why someone might move from Mounjaro to Wegovy in the first place

People arrive at this decision from different directions. Some have responded well to tirzepatide but face a supply gap, a cost change, or a prescriber's recommendation to try a different approach. Others found the side-effect profile of Mounjaro harder to tolerate and want to see whether semaglutide sits differently with them. A smaller group are considering whether Wegovy's newer 7.2mg dose (which the MHRA approved as a dedicated single-dose pen in April 2026) brings them closer to the results tirzepatide had been delivering.

None of these are wrong reasons. What matters is that the switch is planned carefully rather than made impulsively, because the two medicines work through partly overlapping but not identical pathways. Mounjaro activates both the GLP-1 and GIP receptors; Wegovy activates GLP-1 alone. That distinction shapes how each medicine affects appetite, gastric emptying and blood sugar, and it means your body will be adjusting to a meaningfully different drug, not simply a rebranded version of the same one.

Before reaching for the phone to request a switch, one useful habit: pull up your most recent weight log and note the trend over the last eight weeks. If loss has slowed significantly, that context will be directly relevant to the conversation with your prescriber, and it takes under a minute to check.

What the evidence shows when you compare the two medicines head to head

The clearest data we have comes from SURMOUNT-5, a 72-week open-label trial published in the New England Journal of Medicine in 2025, in which tirzepatide produced a greater average weight reduction than semaglutide 2.4mg in adults with obesity and no diabetes. Mounjaro's SURMOUNT-1 trial, also published in the New England Journal of Medicine, showed average body-weight reductions of around 20–21% at the 15mg dose over 72 weeks. Wegovy at 2.4mg produced around 15% average loss in the STEP 1 trial over 68 weeks.

The gap narrows with Wegovy's higher dose. Trials of the 7.2mg maintenance dose reported average weight loss of around 20.7% over 72 weeks, approaching what tirzepatide achieved at its top dose. So if you were doing well on Mounjaro 15mg and are considering a switch, whether Wegovy can match those results after tirzepatide is a genuine and reasonable question, one the SURMOUNT-5 data begins to address, though it does not directly study people who have already used one medicine and then switched to the other.

The table below summarises the headline factual differences between the two medicines as licensed in the UK.

Both medicines carry the same broad eligibility criteria for private prescription. A fuller side-by-side look at the two treatments covers eligibility, side effects and cost context in more depth.

What to expect during the transition itself

Switching is not as straightforward as resuming at whatever dose you were taking of Mounjaro. Most clinical guidance suggests starting Wegovy from a lower dose when changing from one GLP-1 or dual-agonist medicine to another, to give your system time to adjust to the different molecule. Your prescriber will advise on the appropriate starting point based on how long you have been off Mounjaro, your current weight and any side effects you experienced.

The gastrointestinal side-effect profiles of both medicines overlap considerably (nausea, loose stools, constipation and reflux are common to both, particularly around dose changes) so a period of re-adjustment is expected even if you tolerated Mounjaro well. It does not mean the switch is not working. The practical steps involved in moving from one medicine to the other are worth reading through before you make the decision, so you go in with realistic expectations. The NHS medicines information for both tirzepatide and semaglutide describes the full side-effect profile and the circumstances in which you should seek medical help promptly.

For some people, the reverse journey is also on the table. If you have tried Wegovy previously and are now looking at returning to Mounjaro, the same principle applies: a fresh prescriber review, not an assumption that you can simply pick up where you left off.

How to approach the conversation with a prescriber

This is ultimately a clinical decision, and one where context matters enormously. A prescriber will want to know how much weight you lost on Mounjaro, at what dose, over how long; whether you stopped or are still taking it; why you want to switch; and your current BMI and health picture. Framing the conversation around your goals rather than a specific product request tends to produce more useful clinical input.

At nume, our clinical team reviews every consultation personally. If you are transferring from another treatment, our prescribers ask for evidence of your current regimen and dose before making any recommendation. That is not bureaucracy, it is the basis for a safe, informed decision. Cost differences between the two treatments are worth factoring in too, though they should sit alongside the clinical picture rather than drive it.

Which medicine suits you after a course of Mounjaro is a clinical decision our prescribers make with you. Speak to our prescribers through a free consultation and we will review your situation the same day.