Transitioning from Mounjaro to Wegovy: what the evidence says

The biggest misconception: switching is not just swapping one injection for another

A question our prescribers hear most weeks goes something like this: "I'm on Mounjaro 10mg, can I just move straight to Wegovy 2.4mg?" The assumption is that both medicines do roughly the same job, so matching doses is straightforward. It is not quite that simple, and understanding why matters before you make any decision.

Mounjaro (tirzepatide) activates two gut-hormone receptors, GIP and GLP-1, which is why it is described as a dual agonist. Wegovy (semaglutide 2.4mg) works on the GLP-1 receptor only. Both slow gastric emptying and reduce appetite, but they do so through different receptor pathways, which means individual responses can differ meaningfully. Someone who loses significant weight on one may respond differently to the other, and vice versa, a point backed by the head-to-head data in the SURMOUNT-1 trial published in the New England Journal of Medicine and the broader SURMOUNT-5 findings, where average outcomes differed at a population level but individual variation was real. There is also emerging evidence that some people do respond better to semaglutide than tirzepatide, which you can read about in more detail on our page covering whether semaglutide suits some patients better.

Crucially, dose equivalence between the two medicines has not been established in a clinical protocol. A prescriber cannot simply translate your current Mounjaro dose into a Wegovy dose by looking at the numbers. The titration schedules are different, the receptor profiles differ, and your body's tolerance on one tells a prescriber only so much about where to start on the other. Starting at the lowest maintenance-entry dose is the usual cautious approach, though your prescriber will assess your specific situation.

What the medicines look like side by side

Before weighing a switch, it helps to see the two treatments clearly. The table below summarises the factual differences. Numbers for average weight loss come from their respective phase-3 trials and are population averages, not predictions for any individual.

Both medicines carry a Black Triangle (▼) designation in the UK, meaning the MHRA monitors them under enhanced surveillance. The NHS patient information for tirzepatide and the equivalent page for semaglutide cover side-effect profiles in plain language. The GI-led side-effect picture (nausea, changes in bowel habit, indigestion) is similar for both, though individual experience varies. You can compare both treatments in more depth on our Wegovy versus Mounjaro overview.

Reasons people switch, and what clinicians look at

There is no single reason someone moves between these medicines. Some people switch because their current treatment has become unavailable. Others have reached the highest tolerated dose of one and want to explore whether the other pathway produces a different response. Occasionally, side-effect profiles differ enough between individuals that one medicine is better tolerated than the other. Cost considerations arise too, the private price of each medicine varies by dose and changes over time, and a full cost comparison is covered on our tirzepatide versus semaglutide cost page.

When a prescriber assesses a switch from Mounjaro to Wegovy, or the Mounjaro-to-Wegovy transition more broadly, they will look at how long you have been on your current medicine, your current dose, your weight trajectory, any side effects you have experienced, and your overall health picture. For patients already established on treatment, a prescriber may also want to understand what prompted the switch request before recommending one. This is not bureaucracy, it is the clinical step that keeps you safe.

The process of transferring from Mounjaro to Wegovy through a regulated pharmacy like nume involves submitting evidence of your current treatment as part of the consultation. Our prescribers review that evidence before any prescription is written. More about how nume works is on our about page if you want to understand the clinical infrastructure before you start.

Which direction is the right one for you?

The honest answer is: it depends, and that is exactly what a prescriber is for. If you are considering the switch from Wegovy to Mounjaro rather than the other direction, the clinical logic runs in reverse, the dual-agonist pathway may produce a stronger average response at population level, but that does not guarantee it will for you, and you would typically restart titration from a low dose. A detailed look at this specific direction is on our page covering the reverse transition from Mounjaro to Wegovy and the clinical question of whether this switch is appropriate.

What the evidence does not support is the idea that one medicine is simply "better" and that switching will always improve results. SURMOUNT-5 showed greater average weight loss with tirzepatide at the group level, but population averages mask individual variation. Some patients sustain excellent outcomes on Wegovy and have no clinical reason to switch. Others find their weight loss plateaus and a change in mechanism is worth exploring. Which situation describes you is a clinical decision our prescribers make with you, not something a web page can answer. If you are ready to start that conversation, check your eligibility through a free consultation.