Switching from Saxenda to Mounjaro: what actually changes

You're on Saxenda but wonder if it has stopped working, here's the clinical picture

Saxenda contains liraglutide, a GLP-1 receptor agonist injected once daily. It was approved by the MHRA for weight management and many people used it successfully before newer options arrived. If your weight loss has plateaued or you find daily injections difficult to maintain, it is a reasonable question to raise with a prescriber.

Mounjaro is tirzepatide, which activates both the GIP and GLP-1 receptors. That dual action is the reason its trial results differ from earlier GLP-1 medicines. In the SURMOUNT-1 trial (published in the New England Journal of Medicine and covering 72 weeks of treatment) participants on the 15mg dose achieved an average body-weight reduction of around 20 to 21 per cent. Semaglutide, the GLP-1 medicine in Wegovy, produced roughly 15 per cent average loss in its pivotal STEP 1 trial at 68 weeks. Liraglutide (Saxenda) generally sits lower still in direct comparisons, though individual responses vary.

One practical detail worth mentioning: Mounjaro is a once-weekly injection, stored in the fridge door alongside whatever else you refrigerate. For people who found daily Saxenda injections disruptive to their routine, that change alone is meaningful. If you are also curious about what moving from a GLP-1 medicine to tirzepatide involves more broadly, that is worth reading before your consultation. The clinical question is whether you are a suitable candidate for tirzepatide specifically, and that is what a prescriber needs to assess.

For a fuller breakdown of how these two medicines sit alongside each other, the Saxenda vs Mounjaro comparison covers their mechanisms, dosing schedules and licensed indications in more detail.

What Saxenda's licensing status means for you right now

Saxenda (liraglutide) holds a UK licence for weight management and can still be prescribed privately. However, nume does not dispense Saxenda. For weight loss in the UK, the two MHRA-licensed injectable medicines that clinical prescribers at nume work with are Mounjaro (tirzepatide) and Wegovy (semaglutide). Both appear in NICE's appraisal TA1026 and TA875 respectively as recommended options, which is part of why clinical focus has shifted toward them.

If you are currently on Saxenda and considering a switch, the licensed route to Mounjaro is a clinical consultation. The prescriber will look at your current weight, health history, any conditions that might affect suitability, and your experience on liraglutide. They may also consider Wegovy as an alternative if tirzepatide is not appropriate for you. There is no automatic dose-equivalence when switching GLP-1 medicines: your prescriber will set a starting point based on clinical judgement, and Mounjaro's standard starting dose is 2.5mg (a tolerability level while your system adjusts) regardless of what dose you were on before.

To understand what the transition process looks like step by step, see our guide on how to switch from Saxenda to Mounjaro, which covers the practical and clinical considerations your prescriber will walk through with you.

Side effects, eligibility and what the numbers actually mean for you

Both liraglutide and tirzepatide share a GI-led side-effect profile: nausea, loose stools, constipation, indigestion and fatigue are the most commonly reported, particularly at the start of treatment or after a dose increase. These effects are generally mild to moderate and settle over days to a couple of weeks. Because Mounjaro is a newer medicine, it carries a Black Triangle (▼) marker from the MHRA, meaning the regulator actively collects additional safety data. Patients can and should report any suspected side effects via the MHRA Yellow Card scheme.

MHRA guidance also emphasises that GLP-1 medicines are not assessed for quick or cosmetic weight loss, they are prescribed for adults where excess weight poses a health risk. The private-licence eligibility for Mounjaro is broadly BMI 30 or above, or BMI 27 or above with at least one weight-related condition such as hypertension, high cholesterol, type 2 diabetes or obstructive sleep apnoea. If you want to feel confident you are choosing the right provider when you start Mounjaro, it is worth knowing what to look for before you commit. A prescriber assesses the whole picture, not the BMI number alone.

If you have been on Saxenda for some time, a transfer to tirzepatide is not unusual, but it is not automatic either. Evidence of your current treatment, your weight history and your health status all inform the clinical decision. For those who have already tried tirzepatide and are wondering about next steps, our page on switching from Mounjaro to retatrutide sets out what that pathway can look like. Our team explains how that review works on the about us page, and our clinical lead's profile is available at our clinical team page if you want to know who is reviewing your case.

Which medicine is right for you is a clinical decision made with a prescriber who knows your history. If you are ready to explore whether Mounjaro is suitable, the starting point is a free consultation with our clinical team. You can also read more about Mounjaro and how it works before you do.