Mounjaro®
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Start journey Learn moreOzempic vs Mounjaro for weight loss: what the evidence and licensing actually say
The biggest misconception: Ozempic and Mounjaro are not interchangeable weight-loss medicines
The most common misunderstanding our prescribers encounter (genuinely, a question that comes up most weeks) is that Ozempic and Mounjaro are simply two versions of the same thing. They are not. Both involve injections taken once weekly, and both affect appetite. Beyond that, the comparison gets complicated quickly.
Ozempic contains semaglutide, the same active ingredient as Wegovy, but it is licensed by the MHRA exclusively for type 2 diabetes, not for weight management. Prescribing it for weight loss is off-label, and the NHS medicines page for semaglutide is clear on this distinction. If you have been taking Ozempic, it was almost certainly prescribed for blood-sugar control, and any conversation about switching needs to start there, with whoever manages your diabetes, not just a weight-loss clinic.
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist, activating two gut-hormone pathways rather than one. It holds a UK licence for weight management in adults with a BMI of 30 or above, or 27 and above with a weight-related condition, alongside diet and activity changes. You can read more about how the two medicines compare mechanistically on the Mounjaro vs Ozempic overview page. The distinction matters practically: a prescriber considering a switch needs to know why you were originally on Ozempic, whether diabetes management is still a factor, and whether tirzepatide's weight-loss licence fits your situation.
What the trial evidence shows when you compare the two active ingredients
Because Ozempic is not licensed for weight loss, there is no direct regulatory head-to-head between Ozempic and Mounjaro in that setting. The closest comparison comes from SURMOUNT-5, a 72-week open-label trial published in the New England Journal of Medicine (2025) that compared tirzepatide against semaglutide 2.4mg (the Wegovy dose, not the Ozempic doses) in 751 adults with obesity and no diabetes. Tirzepatide produced greater average weight reduction.
| Factor | Tirzepatide (Mounjaro) | Semaglutide 2.4mg (Wegovy) |
|---|---|---|
| Mechanism | Dual GIP + GLP-1 agonist | GLP-1 agonist |
| Average weight loss (SURMOUNT-1 / STEP 1) | ~20–21% at 15mg over 72 weeks (NEJM, SURMOUNT-1) | ~15% at 2.4mg over 68 weeks (NEJM, STEP 1) |
| Head-to-head result (SURMOUNT-5, 72 weeks) | Greater average loss | Comparator |
| UK weight-loss licence | Yes (MHRA, Mounjaro) | Yes (MHRA, Wegovy, not Ozempic) |
| Dose schedule | 2.5mg starter, titrated to up to 15mg by prescriber | 0.25mg starter, titrated to 2.4mg (or 7.2mg) by prescriber |
These numbers come from separate trial populations and conditions, so a direct subtraction is not clinically meaningful. Which medicine produces better results for a specific person depends on tolerance, any other health conditions and how they respond. The full details of Wegovy vs Mounjaro are covered separately if you want to explore the semaglutide side more carefully.
How a switch from Ozempic to Mounjaro would actually work in practice
If you are currently taking Ozempic for diabetes and want to move to a weight-loss medicine, the first conversation belongs with your diabetes team. Stopping or switching a blood-sugar medicine without oversight carries real risk. That is not a bureaucratic hurdle, it is the clinical reality of managing two different conditions that may have overlapped in one injection.
If your diabetes is now well controlled, or if it was never the primary reason for your prescription, a prescriber can assess whether tirzepatide is appropriate. The practical switching guide covers the clinical steps in more detail, including timing and what evidence a prescriber would typically want to see. Separately, if you are already on Mounjaro and considering the reverse direction, the Mounjaro to Ozempic page addresses that question directly.
At nume, transfer patients go through the same same-day clinical review as new patients, a real prescriber reads the consultation, checks evidence of current treatment and dose, and makes a decision based on the full picture. You can explore our weight-loss treatments to see what licensed options are available, or read about switching from Ozempic to tirzepatide more broadly. The treatment overview is also a useful starting point if you are not yet certain which medicine fits your circumstances.
What is actually licensed for weight loss in the UK, and where nume fits
To be clear: at nume, we prescribe for weight management only, and only within licensed indications. Ozempic is not one of them. The two medicines we dispense for weight loss are Mounjaro (tirzepatide) and Wegovy (semaglutide injection). The NICE appraisal of tirzepatide (TA1026) sets out the eligibility criteria the NHS uses; private eligibility mirrors the licensed SmPC thresholds. Lower BMI thresholds can apply for some ethnic backgrounds under UK clinical guidance.
Side effects across both medicines are led by the gastrointestinal system, nausea, loose stools, constipation and indigestion are the most frequently reported, particularly early in treatment or after a dose step. They typically settle within a couple of weeks. Serious effects including pancreatitis are infrequent but warrant urgent attention; the MHRA Yellow Card scheme is the reporting route if you experience something unexpected. For a cost comparison between these two licensed options, the Mounjaro vs Wegovy price page sets out the context honestly. Which medicine is right for you is a clinical decision, one our prescribers make with you, not for you.
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