Mounjaro®
Starting from £179.99/mo
Start journey Learn moreHow Ozempic and Mounjaro actually compare, mechanism, evidence and UK licensing
The myth: Ozempic and Mounjaro are basically the same thing
A question our prescribers hear most weeks: "Can I just switch to whichever is cheaper or easier to get?" The short answer is no, and the reason matters. Ozempic contains semaglutide, a GLP-1 receptor agonist, it mimics one gut hormone involved in appetite and blood-sugar regulation. Mounjaro contains tirzepatide, a dual GIP and GLP-1 receptor agonist, activating two separate hormonal pathways simultaneously. It is the only dual-agonist weight-loss medicine licensed in the UK. Activating both receptors appears to produce a stronger appetite-suppressing and metabolic effect than a single-pathway approach. So while both medicines share a general mechanism (reducing appetite, slowing gastric emptying), they are not interchangeable, and our Ozempic and Mounjaro guide walks through exactly where those differences lie. You can read more about whether Mounjaro and Ozempic are the same medicine for a deeper breakdown of the pharmacology.
Crucially, Ozempic's MHRA licence covers type 2 diabetes management, not weight loss in people without diabetes. Prescribing it specifically for weight management outside that licence is off-label use, and any pharmacy dispensing it that way without a clear clinical rationale should prompt serious questions. If you are weighing up whether Ozempic or Mounjaro is the right option for you, understanding those licensed indications is a good place to start. The NHS medicines page for tirzepatide and the separate NHS semaglutide resource each spell out the licensed indications plainly.
What the evidence actually shows, and what a fair comparison requires
Because Ozempic's licensed comparator for weight loss is Wegovy (also semaglutide, at a higher 2.4mg weekly dose), a fair head-to-head for weight management is Mounjaro versus Wegovy, not Mounjaro versus Ozempic. The SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, directly compared tirzepatide against semaglutide 2.4mg in adults with obesity and no diabetes over 72 weeks. Tirzepatide produced a greater average reduction in body weight. NICE's appraisal of tirzepatide (TA1026) notes that indirect comparisons also favour tirzepatide over semaglutide for weight loss, though the committee cautioned that study populations and designs differ. The earlier SURMOUNT-1 trial (2,539 adults, 72 weeks) reported roughly 20–21% average body-weight reduction at the 15mg maintenance dose. The STEP 1 trial for semaglutide 2.4mg reported around 15% on average over 68 weeks.
A structured look at the key differences is useful here:
| Feature | Ozempic (semaglutide) | Mounjaro (tirzepatide) |
|---|---|---|
| UK weight-loss licence | No) type 2 diabetes only | Yes, BMI ≥30, or ≥27 with a weight-related condition |
| Receptor mechanism | GLP-1 agonist (single pathway) | GIP + GLP-1 dual agonist |
| Average weight loss in trials | ~15% at 2.4mg/week (Wegovy, STEP 1) | ~20–21% at 15mg/week (SURMOUNT-1, NEJM) |
| UK dose range | 0.25mg to 1mg (Ozempic); up to 2.4mg (Wegovy) | 2.5mg to 15mg |
| Maker | Novo Nordisk | Eli Lilly |
| Dispensable by nume for weight loss | No | Yes |
Those numbers come from separate trials with different populations, so direct cross-trial comparisons have limits. For a true head-to-head between the two weight-management-licensed medicines, the Wegovy vs Mounjaro comparison covers SURMOUNT-5 in more detail.
Which one is available for weight loss in the UK, and what that means in practice
If your interest is weight management, the two medicines with full UK licences for that purpose are Mounjaro and Wegovy (semaglutide at 2.4mg and, since April 2026, up to 7.2mg). Ozempic is not one of them. Rybelsus, the oral semaglutide tablet approved for type 2 diabetes, is not one of them either. Seeking Ozempic specifically for weight loss puts you in territory where a legitimate prescriber will need to justify the off-label decision carefully, and where the supply route matters enormously. The MHRA has warned publicly about fake weight-loss pens sold online and via social media; large seizures of counterfeit products (some containing insulin rather than the stated medicine) have resulted in hospitalisations. Always verify any online pharmacy on the GPhC register before ordering anything. Report suspicious sellers via the Yellow Card scheme.
At nume, Mounjaro is the primary weight-management injection we dispense, sourced through the licensed UK supply chain from Eli Lilly. Wegovy is also available. Ozempic is not dispensed for weight loss. If you are currently on Ozempic for diabetes and wondering about switching, that is a conversation to have with your diabetes team first. For context on how the two semaglutide brands relate to each other, this page on switching between Mounjaro and Ozempic covers the practical questions. Our clinical team reviews every consultation personally; a prescriber, not a system, decides what is clinically suitable for you.
Side effects across both semaglutide and tirzepatide share a gastrointestinal character (nausea, loose stools, constipation, indigestion and fatigue are the most commonly reported) typically most noticeable after a new dose and settling over days. Both are prescription-only medicines; both carry Black Triangle (▼) status in the UK, meaning additional MHRA monitoring applies. The cost picture for these medicines is explored separately in a dedicated cost comparison. Which medicine suits you is a clinical decision our prescribers make with you, based on your full health picture, not a product choice you should make from a comparison article alone.
Looking to start your weight loss journey?
Take a quick eligibility quiz to explore your options and see how we can support you.