Mounjaro®
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Start journey Learn moreThe switch decision: four factors that matter clinically and practically
What the clinical trial evidence says, before you read anyone's review
Reviews are subjective; trial data gives them context. In SURMOUNT-1, tirzepatide (Mounjaro) produced average weight reductions of around 20–21% at the 15mg dose over 72 weeks, among thousands of adults with obesity and without diabetes [SURMOUNT-1, New England Journal of Medicine]. The STEP 1 trial found semaglutide 2.4mg (Wegovy) produced around 15% average loss over 68 weeks [STEP 1, NEJM]. When the two were put head-to-head in the SURMOUNT-5 trial (72 weeks, 751 adults with obesity, no diabetes), tirzepatide produced greater average weight reduction than semaglutide 2.4mg, making it the only published randomised head-to-head comparison we have. NICE's appraisal of tirzepatide noted indirect comparisons favour it on weight loss [NICE TA1026].
What reviews frequently add to this picture: some people find Wegovy's GI side effects (nausea, bloating, loose stools) feel gentler at equivalent stages of titration, while others report the opposite. Neither medicine is universally easier to tolerate. That individual variation is exactly why the trial averages don't decide the switch for you.
One quick habit worth building: before reading reviews, check whether the person writing was switching doses at the time. Most GI complaints cluster around dose increases, so a review written on the first week of a new strength tells you about that transition, not the medicine itself at steady state.
Switching from Mounjaro to Wegovy: the patterns people describe
The most consistent theme in reviews from people who switched from Mounjaro to Wegovy is that weight loss slowed. This aligns with the trial data: Wegovy's average outcomes are lower, and switching mid-course resets some of the metabolic progress. People who switched because of Mounjaro supply issues often describe frustration at the pace difference, though many report that Wegovy's nausea felt more manageable for them personally.
A smaller group switched specifically because Mounjaro's cost was higher and found Wegovy sufficient, the cost difference between the two is a real practical factor covered separately. Others report that Wegovy's weekly injection felt similar enough that the transition itself was unremarkable, provided their prescriber set the starting dose carefully.
Crucially, a switch is not a simple like-for-like substitution. The two medicines work via different mechanisms: Mounjaro activates both GIP and GLP-1 receptors, while Wegovy acts on GLP-1 alone. What a prescriber needs to decide is where to enter the Wegovy dose ladder, how long a washout (if any) is appropriate, and whether the reason for switching changes the clinical picture. That decision shouldn't come from a forum thread.
For a fuller clinical breakdown of how the two medicines compare, the Mounjaro vs Wegovy comparison page covers the mechanism and evidence in more detail.
Switching from Wegovy to Mounjaro: what reviews say going the other way
Reviews of the Wegovy-to-Mounjaro switch tend to be more positive about weight-loss outcomes, consistent with the head-to-head data. People moving to Mounjaro after a plateau on Wegovy often describe renewed progress, though a few note that GI side effects were more pronounced in the first few weeks on tirzepatide, particularly around dose increases.
The experience of switching back to Mounjaro from Wegovy varies depending on how long someone has been on semaglutide and at what dose. Prescribers at nume (sorry, at nume) review evidence of current treatment before approving any change; this is part of our standard safety process, not a formality.
If you're considering switching because Wegovy stopped working, that's a different clinical question from switching because of side effects or cost. The answer looks different in each case, and our prescribers will ask about it.
Side-by-side: what the data and licensing actually show
The table below summarises the key factual differences relevant to a switch decision. Numbers are from the cited trial papers and UK regulatory documents; individual results differ.
| Factor | Mounjaro (tirzepatide) | Wegovy (semaglutide 2.4mg) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 receptor agonist | GLP-1 receptor agonist |
| Average weight loss in trials | ~20–21% at 15mg (SURMOUNT-1, 72 weeks) | ~15% at 2.4mg (STEP 1, 68 weeks) |
| Head-to-head result | Greater average loss (SURMOUNT-5, 72 weeks) | Compared to 2.4mg; 7.2mg dose narrows gap |
| UK licence (weight management) | Yes (BMI ≥30, or ≥27 with a weight-related condition | Yes) BMI ≥30, or ≥27 with a weight-related condition |
| Injection frequency | Once weekly | Once weekly |
| NICE recommendation | TA1026 (Dec 2024) (BMI ≥35 + ≥1 comorbidity for NHS | TA875 (Mar 2023)) within specialist services, max 2 years |
Both medicines are Black Triangle (▼) products under additional MHRA monitoring. Neither should be started or switched without a clinical assessment. If you've been on Mounjaro and are curious about moving to Wegovy, or vice versa, the practical guide to making the switch covers the steps involved, and our prescribers assess every request individually. The Wegovy vs Mounjaro page approaches the same comparison from a different angle if you want a second read.
Which medicine suits you (and whether a switch makes clinical sense at this point) is a decision made with a prescriber who knows your full history. Our clinical team reviews every case; you can start a free consultation to have that conversation today.
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