What's semaglutide, and why are so many people asking about it?

Step 1: what semaglutide is doing inside the body

The name semaglutide refers to a synthetic version of GLP-1 (glucagon-like peptide-1), a hormone your gut releases naturally after eating. GLP-1 travels to the brain's appetite centres and signals that you've had enough; it also slows the rate at which your stomach empties, so food sits with you longer. Semaglutide replicates and extends that signal far beyond what a meal-triggered GLP-1 pulse would achieve. Because it's been modified to resist the enzyme that normally breaks GLP-1 down quickly, a single weekly injection keeps those receptors activated throughout the week.

The practical result is that hunger becomes quieter. Many people describe eating smaller portions without effort, losing interest in snacking, and feeling full well before finishing a meal. That shift happens at a biological level, the drive to eat is being modulated, not just resisted by willpower. The full clinical picture of semaglutide covers how this translates across different patient groups.

What's in semaglutide, precisely? The active molecule is the GLP-1 analogue itself, alongside standard pharmaceutical excipients, a phosphate buffer, propylene glycol, phenol as a preservative, and water for injections, as listed in the Wegovy SmPC. The tablet formulation adds SNAC (sodium N-(8-[2-hydroxybenzoyl]amino)caprylate) as an absorption enhancer, which is what makes oral delivery possible. If you want the full ingredient detail, the Wegovy ingredients page breaks this down.

Step 2: the licensed routes, injection and tablet, weight loss and diabetes

There's a lot of confusion about what semaglutide is sold as and why. The short version: the molecule is the same, but the product, dose, and licence vary depending on what it's treating.

For weight management, semaglutide is licensed in the UK as Wegovy, the injection, titrated from 0.25mg up to a maintenance dose of 2.4mg weekly, with a higher 7.2mg option approved by the MHRA in April 2026 for adults with a BMI of 30 or above. The Wegovy tablet, approved in June 2026 and the first oral GLP-1 weight-loss medicine in Europe, works up to a 25mg daily maintenance dose. Neither of these is the same product as Ozempic, which uses lower doses of the same molecule specifically for type 2 diabetes management and is not licensed for weight loss. Rybelsus, the oral semaglutide tablet for diabetes, uses the same SNAC absorption mechanism as the Wegovy tablet but at diabetes doses (3mg, 7mg, 14mg), an entirely separate licence again. The guide to semaglutide's brand names untangles these if the overlap is still confusing.

For weight management specifically, the NHS notes that semaglutide (Wegovy) is prescribed alongside a reduced-calorie diet and increased physical activity, it isn't a standalone fix, and trials are always conducted with lifestyle support in place.

Step 3: who the evidence says it works for, and what results look like

The STEP 1 trial (1,961 adults with obesity or overweight plus a weight-related condition, no diabetes, 68 weeks) found an average body-weight reduction of around 15% with semaglutide 2.4mg against roughly 2.4% with placebo. That figure is a mean across the whole trial population; individual results spread around it. NICE recommended Wegovy (TA875) within specialist weight management services for adults with a BMI of 35 or above and at least one weight-related condition, with treatment running for a maximum of two years. BMI thresholds are 2.5 kg/m² lower for South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds under UK guidance.

The newer 7.2mg injection dose, studied over 72 weeks, brought average weight loss to around 20.7%, narrowing the gap with tirzepatide. For anyone curious how the two medicines compare, the comparison with newer agents is worth reading once you've got the basics here. Eligibility for private treatment follows the licensed criteria: a BMI of 30 or above, or 27 or above with at least one weight-related condition such as high blood pressure, high cholesterol, or obstructive sleep apnoea. A prescriber reviews the complete picture before anything is authorised, BMI alone is not a rubber stamp.

Side effects worth knowing before you ask for a prescription

The most common side effects are gastrointestinal: nausea, vomiting, diarrhoea, constipation, and indigestion are the ones patients mention most often. They tend to be at their worst just after starting or after a dose increase, and most people find they ease within a couple of weeks as the body adjusts. Starting low and titrating slowly (the whole point of the escalation schedule) is specifically designed to reduce this burden.

A few things need prompt medical attention. The MHRA issued a Drug Safety Update in January 2026 highlighting acute pancreatitis as an infrequent but serious risk: severe, persistent stomach pain that spreads to the back, with or without vomiting, is a signal to get medical help the same day rather than wait. Gallbladder symptoms, signs of significant dehydration from prolonged vomiting or diarrhoea, and any allergic reaction (swelling, breathing difficulty) also warrant urgent review. You can report any suspected side effect directly to the MHRA via the Yellow Card scheme. Timing of doses matters too, if you'd like to understand when in the day to take your injection, the guide on Wegovy timing covers the practicalities.

Semaglutide is not recommended during pregnancy, while breastfeeding, or when trying to conceive. It isn't licensed for under-18s. Anyone with a history of pancreatitis or certain rare thyroid conditions should discuss this with a prescriber before starting. The conversation matters, and it's the first thing that happens when you check your eligibility with our clinical team.