Ozempic vs semaglutide for weight loss: same molecule, very different licences

Why the STEP trials were run under Wegovy, not Ozempic

The clearest way to understand the ozempic-versus-semaglutide-for-weight-loss debate is to start where the regulators started: the clinical trial programme. The pivotal STEP 1 trial, published in the New England Journal of Medicine, enrolled adults with obesity or overweight who did not have diabetes. Over 68 weeks, participants on semaglutide 2.4 mg achieved an average body-weight reduction of around 15%. The dose matters: 2.4 mg weekly is the maintenance dose studied in STEP 1 and the dose on the Wegovy label. Ozempic's highest approved dose for diabetes is 2 mg weekly, and the 0.5 mg and 1 mg doses used earlier in diabetes management were never studied as weight-management doses in large outcome trials.

The MHRA licensed Wegovy for weight management in the UK on the strength of this programme. Ozempic's UK licence covers glycaemic control in type 2 diabetes, a separate regulatory assessment for a separate clinical purpose. When clinicians and researchers compare semaglutide versus Ozempic for weight loss, they are, in effect, comparing a licensed weight-management medicine against a diabetes medicine used outside its approved indication. That context shapes every number in the comparison.

A brief note on Rybelsus: oral semaglutide tablets at 3 mg, 7 mg and 14 mg also carry a diabetes licence, not a weight-loss one. The oral semaglutide tablet approved for weight management in the UK is the Wegovy tablet at a 25 mg maintenance dose, a clinically and regulatorily distinct product, and our semaglutide peptide vs Ozempic page explores how these various forms of the molecule compare.

What the licences actually permit, and what they prevent

NHS guidance on semaglutide explains the position plainly: Ozempic is not a weight-loss medicine in the UK. NICE's appraisal of semaglutide for weight management (TA875) specifically evaluated Wegovy, not Ozempic, and its recommendations on eligibility thresholds, two-year treatment limits, and specialist service requirements apply to Wegovy alone. A GP or online prescriber acting within their professional duties cannot simply substitute one for the other.

This is not a technicality. The two products have different approved dose schedules, different patient populations in the supporting evidence, and different commissioning frameworks on the NHS. For someone asking whether Ozempic or semaglutide would help them lose weight, the honest answer is that Wegovy (semaglutide at its licensed weight-management dose) is the one with a regulatory green light for that purpose.

The table below sets out the key factual differences between the two products. Note that only Wegovy is available as a weight-loss treatment through a regulated UK private pharmacy such as ours.

Which licensed weight-loss medicine might suit you, and how that decision is reached

For people who arrive at this comparison genuinely wondering which semaglutide product to use for weight loss, the practical field narrows to Wegovy. The secondary question many then ask is how Wegovy compares with Mounjaro (tirzepatide), since tirzepatide is a dual GIP and GLP-1 receptor agonist, the only one of its kind licensed for weight management in the UK. The SURMOUNT-5 trial, published in the New England Journal of Medicine in 2025, compared tirzepatide directly with semaglutide 2.4 mg over 72 weeks in adults with obesity who did not have diabetes; tirzepatide produced greater average weight reduction. NICE's appraisal of tirzepatide (TA1026) notes that indirect comparisons also favour tirzepatide. That said, both medicines are clinically significant, and the right choice depends on individual medical history, tolerability, current medications, and other factors a prescriber weighs. More detail on that comparison is on our Wegovy versus Ozempic page.

Side effects across both licensed semaglutide and tirzepatide products are predominantly gastrointestinal: nausea, loose stools, constipation, reflux. They tend to be most noticeable after starting or following a dose increase and usually settle within a week or two. Anyone who develops severe, persistent stomach pain (particularly pain that reaches through to the back) should seek medical help promptly; the MHRA highlighted acute pancreatitis as a known, infrequent but serious risk associated with GLP-1 medicines. Suspected side effects can be reported at the MHRA's Yellow Card scheme.

If you're trying to figure out the right moment to start, practically speaking, there's no medically ideal day of the week. Some people find Monday orders suit their routine; others time their first pen around payday or before a holiday. The clinical review happens the same day regardless. What matters is that you're assessed properly before anything is dispatched.

Our prescribers review the full picture (not just a BMI figure) before recommending Wegovy or Mounjaro. You can explore both options and begin a free consultation at our weight-loss treatments page, or read more about current Wegovy pricing at our Wegovy prices page. If you're specifically curious about how the two semaglutide brands sit alongside each other in more detail, our semaglutide vs Ozempic page covers that ground. And if you're already on Ozempic for diabetes and wondering about switching, the switching from Ozempic to Wegovy page is worth reading first. Which option suits you is a clinical decision our prescribers make with you.