Semaglutide INN: the active ingredient behind Wegovy and what the clinical evidence shows

Why the INN matters: semaglutide is not one single product

International Non-Proprietary Names exist so that clinicians, pharmacists and patients can talk about the active substance precisely, without brand loyalty clouding the conversation. For semaglutide, that precision is genuinely useful, because the same molecule sits inside three separate UK-licensed medicines with meaningfully different indications and dose schedules.

Wegovy (semaglutide 2.4 mg injection, now also available up to 7.2 mg) is licensed for weight management in adults with a BMI of 30 or above, or 27 and above where a weight-related condition is present. Ozempic is the same molecule but dosed differently and licensed solely for type 2 diabetes. Rybelsus is an oral tablet form of semaglutide, again for type 2 diabetes only. A misconception that surfaces regularly is that these are interchangeable, they share an INN, so surely they do the same job? They do not. The licensed indication, the dose, and the formulation are distinct. Prescribing Ozempic for weight loss, for instance, would be off-label, and the NHS patient information for semaglutide is clear on what each brand is intended for.

The newest addition to the semaglutide family is the Wegovy tablet. Approved by the MHRA on 11 June 2026, it is the first oral GLP-1 medicine licensed in the UK for weight management, starting at 1.5 mg and escalating to a 25 mg maintenance dose. The INN is still semaglutide; the formulation, absorption mechanism and dosing ladder are entirely different from the injection.

What the controlled trial evidence says about semaglutide for weight loss

The weight-management evidence base for semaglutide was built on the STEP programme, a series of phase-3 trials using the 2.4 mg weekly injection. STEP 1, published in the New England Journal of Medicine, enrolled adults with obesity or overweight plus at least one weight-related condition (no diabetes) and followed them for 68 weeks. Those receiving semaglutide 2.4 mg lost an average of around 15% of body weight, compared with around 2.4% in the placebo group.

Those figures were central to NICE's positive recommendation under TA875, though NICE's NHS criteria attach additional conditions, specifically, that semaglutide is used for a maximum of two years, within a specialist weight management service with multidisciplinary support. That restriction applies to the NHS pathway; private prescribing follows the SmPC's licensed eligibility criteria. Since then, the MHRA has approved a 7.2 mg maintenance dose, with a dedicated single-dose pen cleared on 14 April 2026, and you can find a full breakdown of what that step up involves on our semaglutide 3 page. Trials at this higher dose reported average weight loss of around 20.7% over 72 weeks, which narrows the gap with tirzepatide's results at its highest licensed dose.

The oral form's evidence comes from the OASIS 4 trial, which found an average weight reduction of around 13.6% over 64 weeks versus approximately 2.4% on placebo. Among participants who adhered fully throughout, the figure rose to around 17%. Context for both injection and tablet figures: they were achieved alongside a reduced-calorie diet and increased physical activity, which the licence requires. Neither number should be read as what happens on the medicine alone. You can read more about how the two forms compare on our Wegovy overview page.

How the prescriber uses the INN when assessing your suitability

When a prescriber receives your consultation, they think in INNs, not brand names. That matters practically. If you have ever taken semaglutide under any brand, for any reason, that history is relevant: prior use, current dose, any side effects, and any concurrent medicines all inform the assessment. The most clinically significant interaction for semaglutide concerns other medicines that slow gastric emptying, and the general class effect of delayed absorption for oral medicines taken alongside it.

Safety considerations the prescriber weighs include a personal or family history of medullary thyroid carcinoma, pancreatitis, or certain gastrointestinal conditions. Pregnancy, breastfeeding and actively trying to conceive are situations where semaglutide is not recommended. It is not licensed for under-18s. In January 2026 the MHRA issued a Drug Safety Update for GLP-1 medicines, flagging that severe, persistent stomach pain radiating to the back warrants urgent medical attention as a symptom of acute pancreatitis, a known but infrequent risk. Any suspected side effect can be reported via the Yellow Card scheme.

Understanding the INN also helps you read your prescription accurately: if your prescription says "semaglutide 2.4 mg" rather than "Wegovy", that is not an error. The active substance and dose are what the prescriber has assessed and approved, and our semaglutide 2 page explains in detail what treatment at that dose level typically involves. Questions about what that means for your specific treatment are best put to your prescriber at the time of consultation rather than inferred from brand-name packaging. If you want to understand the cost picture for private semaglutide treatment, our Wegovy price page sets that out plainly.

Getting a semaglutide prescription through a regulated UK route

Because semaglutide (in its weight-management forms) is a prescription-only medicine, the only lawful route to obtaining it is via a prescriber who has conducted a proper clinical assessment. At nume, every consultation is read by a GPhC-registered Independent Prescriber on the same day it is submitted. That review is personal, a real clinician, not automated triage. If you are clinically suitable, treatment is dispatched the same day for free next-working-day tracked delivery.

If you are considering switching from one semaglutide brand to another, or moving from the injection to the tablet form, that decision belongs in a prescriber conversation, not in a self-directed change, and our semaglutide 1 page is a helpful starting point if you are new to treatment and want to understand what the initial dose stage looks like. Our semaglutide guide covers the broader treatment landscape, and our FAQs page addresses common questions about the consultation process. For anything specific to your circumstances, our team is available seven days a week. When you are ready to take the next step, speak to our prescribers through a free consultation.