Has Anyone Switched from Mounjaro to Wegovy — and What Actually Happens?

You're on Mounjaro and wondering whether Wegovy might be a better fit

It's a question our prescribers hear regularly. Perhaps your weight loss has plateaued on Mounjaro, or side effects have been trickier than expected, or your circumstances have changed and you'd like to reassess. Some people come the other way, too, having switched from Wegovy to Mounjaro and wanting to understand that direction instead. Either way, the curiosity is entirely reasonable.

Mounjaro (tirzepatide) activates two gut-hormone receptors, GIP and GLP-1. Wegovy (semaglutide) targets GLP-1 alone. That difference in mechanism is one reason the trial data diverge. In SURMOUNT-1, participants on tirzepatide at the highest dose lost an average of around 20–21% of their body weight over 72 weeks, according to results published in the New England Journal of Medicine. STEP 1, the equivalent semaglutide 2.4mg trial, produced an average of around 15% over 68 weeks. The SURMOUNT-5 head-to-head trial confirmed, in 2025, that tirzepatide produced greater average weight reduction than semaglutide 2.4mg directly compared. Those are averages across thousands of participants, individual results vary considerably.

None of that means Wegovy is the wrong choice. For some people, tolerability matters more than peak efficacy. For others, specific health circumstances or the newly approved 7.2mg Wegovy dose changes the calculation. A quick way to organise your thinking before a consultation: jot down your current dose, how long you've been on it, what's prompted the question, and any side effects. That takes under a minute and makes the clinical conversation much more useful.

What changes (and what doesn't) when you switch

A switch between these two medicines is not a like-for-like substitution. They start at different doses, escalate differently, and the restart process matters. Both treatments begin at a low tolerability dose and step up on roughly four-weekly intervals as directed by the prescriber; you can't map a Mounjaro dose directly onto a Wegovy equivalent. The practical process of switching involves a clinical review of where you are in treatment before any new pen is issued.

The side-effect profile overlaps heavily. Nausea, constipation, bloating, and occasional dizziness are common with both, most pronounced at the start of treatment or after a dose increase, and generally settling over days to a couple of weeks. Some people find one tolerability profile easier than the other, but there's no reliable way to predict that in advance. Worth knowing: if you've struggled with nausea on Mounjaro, it doesn't automatically follow that Wegovy will be kinder, the GI effects are a class characteristic, not unique to either brand.

People who have switched from Mounjaro to Wegovy and then find hunger returning after moving to Wegovy sometimes attribute it to the single-receptor mechanism; others adapt within a few weeks. Both are Black Triangle medicines under additional MHRA monitoring, meaning side effects should be reported via the Yellow Card scheme.

A direct comparison of Mounjaro and Wegovy on the facts that matter for switching

The table below sets out the key differences relevant to someone weighing a switch. Numbers are sourced from the trial data and UK licensing information.

For a fuller breakdown, the Wegovy vs Mounjaro comparison page covers both medicines in detail. The differences between semaglutide, tirzepatide and retatrutide page goes deeper on the mechanism if that's the angle you're exploring.

How the clinical decision actually gets made

A prescriber switching your treatment will want to know at minimum: your current dose and how long you've been on it, how much weight you've lost so far, what's driving the request to switch, and whether you have any conditions that make one medicine more or less suitable. NICE guidance on both medicines, including TA1026 for tirzepatide, sets out eligibility criteria, but private prescribing works within the licensed indications, which for both medicines include adults with a BMI of 30 or above, or 27 or above with a weight-related health condition. Lower thresholds apply for some ethnic backgrounds under UK guidance.

Cost sometimes factors into the decision. The cost comparison between the two is worth reading separately, as pricing has shifted since Eli Lilly revised Mounjaro's UK list price in September 2025. At nume, one price covers the consultation, prescription, treatment and aftercare, no subscription, no tier of extras. We're not positioned as the cheapest option; that's a deliberate choice, because for a prescription medicine, price is the wrong test.

If Wegovy's injectable format appeals but the needle puts you off, the weight-loss treatments page covers all current options available through nume, including oral semaglutide (Wegovy tablets), approved by the MHRA in June 2026. Which suits you is a clinical decision our prescribers make with you.