Switching from Mounjaro to Wegovy: what to expect

Step 1 — understanding why the switch happens in the first place

People move from Mounjaro to Wegovy for a handful of reasons: supply issues, a clinical decision about tolerability, a change in what a prescriber thinks is the right fit, or a cost review. Occasionally, someone starts on one medicine and finds the side-effect profile of the other more manageable. Whatever the reason, it helps to know that Mounjaro (tirzepatide) and Wegovy (semaglutide) are related but not identical. Mounjaro activates two receptors (GIP and GLP-1) which is part of why its average weight-loss figures in clinical trials ran higher than semaglutide's. The SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, found tirzepatide produced greater average weight reduction than semaglutide 2.4mg over 72 weeks among adults with obesity and no diabetes. Wegovy works through the GLP-1 pathway only. That single-pathway difference means your appetite suppression, gastric emptying rate and the hormonal signals involved in fullness may all shift when you change medicines. Some people notice the transition quickly; others take a few weeks to feel the difference. Neither outcome is wrong, bodies vary.

Step 2, how dosing is reset, and why you can't simply carry over your Mounjaro dose

This is where a lot of confusion arises. There is no direct dose equivalence between tirzepatide and semaglutide. If you were stable on, say, 10mg of Mounjaro, that number doesn't translate to a matching Wegovy pen. Wegovy's licensed schedule starts at 0.25mg and titrates upward through 0.5mg, 1.0mg, 1.7mg and 2.4mg, with a recently approved 7.2mg maintenance dose following the MHRA's approval of the single-dose 7.2mg pen in April 2026. In most cases a prescriber will restart from a lower dose on Wegovy, even if you were well-established on Mounjaro, to let your system adjust to the new mechanism. Starting too high carries a genuine risk of more pronounced nausea, vomiting or diarrhoea. Your prescriber sets the starting point based on your individual history. The dose and timing detail for this switch is worth reading before your consultation. And if you have ever wondered about taking both at the same time, the answer is clear: combining Mounjaro and Wegovy is not clinically appropriate and carries serious risks.

Step 3 (managing the physical transition, pen technique and routine

Wegovy and Mounjaro are both subcutaneous injections, but the pens themselves differ in design) the needle gauge, click mechanism and auto-injection style are not the same, so your technique will need a short adjustment even if you are already comfortable with injections. One practical note: both medicines need to be kept refrigerated at 2–8°C, so your pen will still live in the fridge, but check the specific room-temperature guidance in your Wegovy Patient Information Leaflet because the window differs from Mounjaro's and the leaflet is the binding reference. Whether Wegovy needles are the same as Mounjaro's is a question worth settling before your first injection. Injection sites remain the same three areas (abdomen, thigh or upper arm) and rotating between them still matters. On the side-effect front, GI symptoms (nausea, loose stools, constipation, reflux) are common to both medicines and often more noticeable after a dose increase or after restarting at a new dose level. They typically settle within one to two weeks. If you experience severe, persistent stomach pain that spreads to your back, seek medical help promptly, this applies to any GLP-1 medicine and the MHRA's safety communications are explicit on that point.

How the two medicines compare side by side

The table below summarises the key factual differences relevant to anyone considering or managing a switch. Numbers from clinical trials are cited; your personal results will differ.

For a fuller breakdown of costs on the private route, the Mounjaro and Wegovy price comparison sets out what the market looks like. Which medicine suits you is a clinical decision our prescribers make with you, the table above is a starting point for that conversation, not a conclusion. Check your eligibility to start a free consultation with our team.