From Mounjaro to Wegovy: What Changes When You Switch?

The situation: you're on one injection and wondering whether the other would work better for you

It happens more than you'd think. Someone has been on Mounjaro for several months, weight loss has plateaued earlier than expected, or their circumstances have changed and cost is a bigger factor. Someone else has been on Wegovy, lost a steady amount, but read about the SURMOUNT-5 head-to-head trial and wants to know whether tirzepatide would have taken them further. These are reasonable clinical questions, and the answer starts with understanding what each medicine actually does.

Mounjaro (tirzepatide, made by Eli Lilly) activates two gut-hormone receptors: GIP and GLP-1. Wegovy (semaglutide, made by Novo Nordisk) activates one: GLP-1 only. Both slow gastric emptying, reduce appetite and support weight loss alongside a reduced-calorie diet. The dual mechanism of tirzepatide is why, across the clinical programme, it has tended to produce larger average reductions. That doesn't automatically make it the right choice for every individual; it's one factor in a wider clinical picture.

If you're thinking through the switch, you'll find that moving from Mounjaro to Wegovy involves considerations around where you currently are in your titration, how long you've been at your current dose and your full medical history. A prescriber needs to assess all of that before anything changes.

What the trial data actually shows side by side

The clearest comparison comes from SURMOUNT-5, a 72-week open-label trial published in the New England Journal of Medicine in 2025 that put tirzepatide directly against semaglutide 2.4mg in 751 adults living with obesity and no diabetes. Tirzepatide produced greater average weight reduction across all doses tested. NICE cited indirect comparisons favouring tirzepatide when it recommended tirzepatide (TA1026) for NHS use in December 2024.

Wegovy is catching up at its highest dose. The MHRA approved a 7.2mg maintenance dose in January 2026 (and a dedicated single-dose 7.2mg pen in April 2026), with trials reporting around 20.7% average weight loss over 72 weeks, approaching tirzepatide's 15mg results. If you're also wondering whether you can go from Mounjaro to Wegovy, that context matters when the gap between the two medicines looks smaller than the headlines suggest.

Both medicines are Black Triangle (▼) products under additional MHRA monitoring. Neither is suitable during pregnancy, breastfeeding or when trying to conceive, and neither is licensed for under-18s. The NHS medicines pages for tirzepatide and semaglutide carry the full side-effect and contraindication information; the profiles are similar, both led by gastrointestinal effects that tend to settle after the first few weeks at a new dose.

One practical difference worth knowing before you switch

The fridge door situation is identical for both: each medicine needs refrigerated storage at 2–8°C, and you should always check the Patient Information Leaflet for the exact room-temperature window if you're taking a pen away from home. That's not what separates them.

The practical difference that catches people out is the oral contraceptive interaction. For tirzepatide specifically, if you take the pill you should use an additional non-oral method of contraception during the first four weeks of treatment and for four weeks after every dose increase, because absorption of oral hormonal contraceptives may be reduced. NHS guidance notes there is no equivalent evidence of that effect with semaglutide. If you're looking at what it takes to change from Mounjaro to Wegovy, that obligation changes. If you're going the other way, it begins. Your prescriber will flag this, but it's worth knowing before the conversation.

Cost is another practical consideration many people are thinking about. If you want to understand why Wegovy is typically priced differently from Mounjaro in private practice, the reasons are worth reading through separately rather than treating price alone as the deciding factor. For a prescription medicine, the cheapest listing answers the wrong question.

How a switch is handled at nume, and when it makes clinical sense

Every repeat or change at nume is re-reviewed by a GPhC-registered prescriber before anything is dispensed. A switch between Mounjaro and Wegovy isn't treated as a minor amendment; it's a fresh clinical assessment. Our prescribers look at your current dose, how long you've been on it, what results you've seen, and any medical factors that might make one medicine a better fit than the other going forward.

Semaglutide holds a NICE recommendation for weight management (TA875) via specialist NHS services for up to two years. Tirzepatide's NICE approval (TA1026) has a different eligibility structure. Neither recommendation constrains what a private prescriber may consider appropriate, but the evidence behind both informs every consultation our team runs. You can read more about the full landscape of weight-loss treatments we work with, or go straight to starting your free consultation to speak to our prescribers about your situation directly.

If you're mid-treatment and already thinking through the practical steps, the pages on going from Mounjaro to Wegovy and on how the swap works cover the process in more detail. Which medicine suits you is a clinical decision our prescribers make with you.