Semaglutide prescribing information: what the clinical evidence says

What the STEP 1 trial data told prescribers, and what it didn't

The STEP 1 trial, published in the New England Journal of Medicine, randomised 1,961 adults with obesity or overweight plus a weight-related condition to either weekly semaglutide 2.4 mg or placebo, alongside lifestyle support, over 68 weeks. If you want to understand more about how semaglutide works and what it is, that context helps make sense of why the semaglutide group lost an average of around 15% of body weight, with many participants losing more and some losing less. Those figures apply to people who stayed in the trial under those specific conditions, real-world outcomes vary with adherence, dose-tolerance and individual physiology.

One misconception worth clearing up: trial averages are sometimes read as a floor, as though everyone should expect at least 15%. That isn't how the data works. Prescribers use the trial results to explain what is plausible, not to make individual guarantees. The NICE appraisal of semaglutide (TA875) reflects this: if fewer than 5% of body weight is lost after six months on the maintenance dose, continuing treatment should be reviewed. Progress is assessed, not assumed.

For prescribers and patients alike, the trial's most practically useful finding is that consistent weekly dosing with careful titration produced both the results and an acceptable side-effect profile in the majority of participants. That titration schedule is central to safe prescribing, which is why how Wegovy is prescribed in clinical practice follows the same logic the trial was built on.

The dosing schedule prescribers follow, and why it matters clinically

Semaglutide for weight management is not taken at the treatment dose from day one. The licensed schedule starts at 0.25 mg once weekly for the first four weeks, then steps up through 0.5 mg, 1.0 mg and 1.7 mg at roughly four-week intervals, reaching 2.4 mg at around week 16. This is a tolerability pathway, not a therapeutic delay; the gradual increase is what keeps gastrointestinal side effects manageable for most people.

In April 2026, the MHRA approved a higher 7.2 mg maintenance dose for adults with a BMI of 30 or above, initially delivered as three 2.4 mg injections per week and then via a dedicated single-dose pen. The MHRA's announcement of the 7.2 mg pen approval confirmed it is indicated only for the obesity BMI threshold, not the lower cardiovascular indication. Prescribers titrate to 7.2 mg only after the patient has reached and tolerated 2.4 mg.

Semaglutide is a prescription-only medicine, so a prescriber decides not just which dose to start at but whether to hold at any rung if side effects are significant, and when and whether to escalate. The full Wegovy treatment overview covers what that process involves in practice. Patients reviewing semaglutide prescribing information before their consultation should understand that the schedule a prescriber sets is individual, it cannot be self-adjusted based on trial averages.

Who UK prescribing criteria cover, and what NICE recommends

The SmPC licensing threshold for Wegovy is a BMI of 30 or above, or 27 to 29.9 with at least one weight-related condition such as type 2 diabetes, high blood pressure, raised cholesterol or obstructive sleep apnoea. Lower BMI thresholds apply for some ethnic backgrounds under UK clinical guidance, typically 2.5 kg/m² below the standard figures.

NICE's recommendation via TA875 is more specific than the licence alone: it applies within a specialist weight management service providing multidisciplinary support, for a maximum of two years, for adults with a BMI of 35 or above and at least one weight-related comorbidity (or 30 to 34.9 where specialist referral criteria are met). That recommendation covers NHS commissioning; private prescribing follows the SmPC thresholds, assessed case by case.

Semaglutide is not recommended during pregnancy, while breastfeeding, or for people trying to conceive. It is not licensed for anyone under 18. Anyone with a history of medullary thyroid carcinoma, multiple endocrine neoplasia type 2, or a personal or family history of pancreatitis should have a careful prescriber discussion before starting. A full summary of Wegovy clinical information covers contraindications in more detail. The prescriber's role is to weigh all of this individually, which is why clinical assessment is not a formality.

Side effects prescribers discuss, and the monitoring that goes with them

The side-effect profile of semaglutide is well-characterised across the STEP trials and the post-authorisation period. Gastrointestinal effects (nausea, diarrhoea, constipation, vomiting, indigestion) are the most commonly reported, and for most people they are most noticeable in the first weeks of a new dose and settle as the body adjusts.

Prescribers highlight several effects that warrant prompt medical attention rather than watchful waiting. Severe, persistent stomach pain that extends to the back, with or without vomiting, can indicate pancreatitis, a known but infrequent serious risk. Gallbladder symptoms, signs of dehydration from prolonged vomiting or diarrhoea, and allergic reactions all require the same promptness. Patients can report suspected side effects directly to the MHRA via the Yellow Card scheme, a step the prescriber should mention at the point of starting treatment.

Contraception is a practical prescribing consideration that is sometimes overlooked. Women taking oral contraceptives should discuss timing with their prescriber, as GLP-1 treatment can affect absorption. HRT users, particularly those on oral formulations, may also want to review this with their doctor. Anyone facing surgery should tell their anaesthetist and surgical team they are taking semaglutide, delayed gastric emptying is relevant to anaesthetic planning.

If you are working through these details ahead of a consultation, the UK prescribing guidelines for Wegovy page goes further on the clinical framework. And if you are comparing semaglutide with other licensed options, the weight-loss treatment overview sets out what is available and how they differ. When you are ready to have your eligibility assessed by a real prescriber, speak to our prescribers through a free consultation.