Semaglutides explained: the UK guide to how they work and what to expect

You've heard 'semaglutide' everywhere, here's what's actually going on

A lot of people arrive at this search after months of hearing about these medicines in the news, from a friend, or from a GP who mentioned them in passing. It can feel like everyone else has figured something out that you're still trying to piece together. That's a reasonable place to be, and this page is here to fill in the gaps plainly.

Semaglutide is a synthetic version of a hormone your gut already makes, called glucagon-like peptide-1 (GLP-1). After a meal, GLP-1 is released naturally to tell your brain you've eaten enough and to slow the movement of food out of your stomach. In people carrying excess weight, that signalling often doesn't fire strongly enough. Semaglutide amplifies it artificially, which is why, for many people on it, the mental noise around food quietens in a way that feels genuinely unfamiliar. That's not a side-effect to push through; it's the mechanism working. You can read more about the biology on our how semaglutides cause weight loss page.

In the UK, semaglutide medicines licensed for weight management are made by Novo Nordisk under the Wegovy brand, one as a weekly injection and one as a once-daily tablet approved by the MHRA on 11 June 2026. The injection has been available privately and through specialist NHS services for longer; the tablet is newer. Both carry a Black Triangle (▼), meaning they are subject to additional MHRA monitoring while post-market evidence accumulates. The NHS patient information page for semaglutide is a reliable starting point if you want the official summary of uses and cautions.

What semaglutides do, and what they don't

The effects of semaglutide build gradually. The starting doses are low not because they're ineffective but because ramping up slowly gives your digestive system time to adjust. Most people find that hunger, and especially the pull towards snacking between meals, reduces meaningfully within the first few weeks at a therapeutic dose. Portion sizes tend to shrink without feeling like a battle.

What semaglutide doesn't do is replace the need for lifestyle change. Clinical trials paired the medicine with a reduced-calorie diet and increased activity, and that context matters for the results. The STEP 1 trial published in the New England Journal of Medicine followed adults with obesity over 68 weeks and reported an average body-weight reduction of around 15% at the 2.4mg maintenance dose, a result that significantly shifted clinical thinking about what medicines could achieve.

It's also worth being clear about what semaglutide is not. Ozempic, widely covered in the press, is semaglutide too, but it is licensed for type 2 diabetes, not weight management. Using it outside that licence for weight loss is not what it's approved for. The types of semaglutides available in the UK differ by brand, licence, dose and format, and the distinction matters both clinically and legally. Similarly, Rybelsus (the older oral semaglutide) is a diabetes medicine, the new Wegovy tablet is a separate product approved specifically for weight management.

Side effects are real and worth knowing about. The most common are gastrointestinal: nausea, diarrhoea, constipation and indigestion are reported frequently, especially in the first weeks after starting or after a dose step. They usually settle. Rarer but serious effects include acute pancreatitis, the MHRA has highlighted this as a known risk; seek urgent help for severe stomach pain that spreads to your back. A full overview of semaglutide side effects is available on our Wegovy page.

Who semaglutides are licensed for in the UK, and the two routes to access them

The licensed eligibility criteria for Wegovy (injection) cover adults with a BMI of 30 or above, or 27 or above alongside at least one weight-related health condition, for example, high blood pressure, raised cholesterol, prediabetes or obstructive sleep apnoea. For the Wegovy tablet, the MHRA approval in June 2026 sets the same thresholds. Lower BMI cut-offs apply for some ethnic backgrounds under UK guidance. A prescriber assesses the whole picture, BMI alone does not confirm suitability.

NICE recommends semaglutide (Wegovy) for eligible adults within specialist NHS weight management services, for a maximum of two years, under NICE technology appraisal TA875. In practice, NHS waiting lists for specialist services are long in most areas, and the strict eligibility thresholds mean many people who would benefit don't currently qualify for NHS treatment. That's the gap private services exist to fill, if you're considering that route, check your eligibility with our prescribers for a free, same-day clinical assessment. There's no obligation and no prescription until a clinician decides it's right for you.

Alternatively, tirzepatide (Mounjaro) activates both GLP-1 and a second receptor called GIP, and is the only dual-agonist weight-loss medicine licensed in the UK. Some people find it useful to compare both options before a consultation; our full semaglutide guide covers that comparison alongside the clinical evidence for each.

The Wegovy tablet: semaglutides in a new format as of summer 2026

The approval of Wegovy tablets by the MHRA on 11 June 2026 made the UK the first country in Europe to license an oral GLP-1 medicine for weight management. For anyone who finds needles a barrier, that's a meaningful development. The tablet is taken once daily, first thing in the morning on an empty stomach, with a small amount of plain water. You wait at least 30 minutes before eating, drinking anything else or taking other oral medicines. No refrigeration is needed, which makes travel simpler.

The OASIS 4 phase 3 trial (307 adults, 64 weeks) reported average weight loss of around 13.6% against around 2.4% for placebo. Among participants who adhered fully throughout the trial, that figure rose to approximately 17%, though that's the fully-adherent subset result, not the overall average. The most common side effects in the trial were gastrointestinal, affecting around 74% of the semaglutide group compared with 42% on placebo, generally mild to moderate and most pronounced early on.

The tablet is not currently available on the NHS, a NICE appraisal would need to take place first. For now, it's a private prescription medicine. If you want to understand how the tablet compares with the injection in more detail, our guide to how semaglutides work covers both formats alongside the underlying science. And for more on semaglutide as a peptide medicine (including what that means practically) there's more there too.