Wegovie: the spelling, the science, and what the evidence says

What the STEP 1 trial actually found, and why the numbers need context

The headline figure most people encounter is roughly 15% average weight loss over 68 weeks, drawn from the STEP 1 study published in the New England Journal of Medicine. That result was recorded in adults without type 2 diabetes, taking semaglutide 2.4 mg alongside a reduced-calorie diet and increased physical activity. Both parts matter: the medicine and the lifestyle changes were tested together, not the medicine alone.

Since then, the MHRA approved a 7.2 mg dose. Trial data for that higher dose reported around 20.7% average weight reduction over 72 weeks, a meaningful step up. For comparison, the SURMOUNT-5 head-to-head trial published in 2025 found that tirzepatide (a dual GIP and GLP-1 receptor agonist sold as Mounjaro) produced greater average weight loss than semaglutide 2.4 mg, though the 7.2 mg dose narrows that difference considerably. Which medicine is appropriate for a given person is a clinical question, not one an article can answer.

One practical habit worth building before your first consultation: pull up the GPhC pharmacy register at pharmacyregulation.org and search for any online provider you are considering. A legitimate UK pharmacy will have a GPhC premises registration number you can verify in under a minute. If a site does not appear on that register, it should not be dispensing prescription medicines to you.

Who the UK licence covers, and where the NHS sits on this

The Wegovy licence covers adults with a BMI of 30 or above, or a BMI of 27 to 29.9 alongside at least one weight-related condition such as high blood pressure, raised cholesterol, type 2 diabetes, or obstructive sleep apnoea. Lower BMI thresholds apply for certain ethnic backgrounds under UK guidance. Meeting those numbers does not automatically mean treatment is appropriate; a prescriber weighs your full medical history, current medicines and any contraindications before deciding.

On the NHS, NICE recommends semaglutide (Wegovy) only within specialist weight management services, for a maximum of two years, and only when a weight-related comorbidity is present alongside a qualifying BMI. Waiting lists for those services are commonly long, which leads many people to explore private weight-loss injection services instead. The private route does not waive the clinical assessment; it removes the waiting list while keeping the prescriber review that the law requires.

Pregnancy, breastfeeding and actively trying to conceive are all situations where Wegovy is not recommended. The same applies to under-18s. Women using oral contraceptives alongside semaglutide should discuss any absorption concerns with their prescriber.

Side effects: what the evidence tells us, and when to act quickly

The most commonly reported effects in clinical trials were gastrointestinal: nausea, vomiting, diarrhoea, constipation and reflux. These were typically most noticeable after starting treatment or following a dose increase, and for many people they settled within a couple of weeks. Fatigue, headache and injection-site reactions also appeared in trial data.

Pancreatitis is a less common but more serious risk. In January 2026, the MHRA issued a Drug Safety Update highlighting acute pancreatitis across GLP-1 medicines. Severe stomach pain that spreads to the back, with or without vomiting, is a reason to stop the injection and seek urgent medical help rather than waiting to see whether it settles. You can report any suspected side effects, and any suspect sellers, directly through the MHRA's Yellow Card scheme.

Gallbladder problems and, in people with diabetes, changes to retinopathy status are also noted in prescribing information. The full list of contraindications and drug interactions sits in the SmPC; any prescriber reviewing your consultation will work through the relevant ones before approving treatment.

Getting a genuine supply: the private prescription route

Because Wegovy is a prescription-only medicine, buying it safely means going through a prescriber and a pharmacy you can verify. The MHRA has warned repeatedly about fake weight-loss pens circulating online and via social media; in October 2025 the first illicit UK manufacturing site producing counterfeit tirzepatide pens was raided, and previous seizures have found counterfeit pens containing insulin rather than the labelled medicine. The risk is not theoretical.

A regulated online service like Wegovy through a GPhC-registered pharmacy starts with a clinical consultation, ID and weight verification, and a same-day review by a GPhC-registered Independent Prescriber. Once approved, treatment is dispensed through a licensed UK supply chain. If you want to understand what to expect from that process before committing, the FAQs page covers the most common questions. For a broader look at how Wegovy weight loss compares with other options, the weight-loss treatments overview is a useful place to start.

On cost: private Wegovy prices vary by dose and provider. As a general steer, a full breakdown of what any legitimate price should include is worth reading before you compare figures. The guide to weight-loss injection costs covers what to watch for. At nume, one price covers consultation, prescription, treatment and next-working-day delivery, no separate fees, no subscription.

If you think Wegovy could be right for you, the appropriate next step is a clinical conversation. Start your free consultation and a prescriber will review your information the same day.