What Novo Nordisk's semaglutide clinical trials actually showed

What STEP 1 measured and why the results matter in the UK

STEP 1 was the foundational phase 3 trial for semaglutide 2.4mg in weight management. Published in the New England Journal of Medicine, it ran for 68 weeks with 1,961 adults who had obesity or overweight plus at least one weight-related condition, but no type 2 diabetes. Participants in the active group received once-weekly semaglutide alongside a reduced-calorie diet and increased physical activity, the same combination that any legitimate prescriber would expect patients to follow.

The headline: roughly 15% average body-weight reduction for the semaglutide group, against about 2.4% for placebo. Nearly 70% of semaglutide participants lost more than 10% of their starting weight. Those are population averages from a controlled setting, not promises, individual responses vary, and the trial was conducted with structured support that reinforces lifestyle change alongside the medicine.

For UK regulators, the data was persuasive enough. NICE recommended semaglutide (Wegovy) under technology appraisal TA875, published in March 2023, for use within specialist weight management services, for a maximum of two years, in adults with a BMI of 35 or above and at least one weight-related comorbidity. Lower BMI thresholds apply for certain ethnic backgrounds. The NICE criteria are strict; private prescribing operates to the licensed SmPC criteria, which cover BMI 30 and above.

The broader STEP programme: different populations, consistent direction

STEP 1 was not the only study. Novo Nordisk designed the STEP programme to look at semaglutide across several distinct groups. STEP 2 enrolled adults with type 2 diabetes (a population where weight loss tends to be more modest) and still showed meaningful reductions. STEP 3 added intensive behavioural therapy to the regimen, pushing average losses higher. STEP 4 examined what happens when semaglutide is withdrawn: weight gradually returns, which tells you something real about how the medicine works and why ongoing clinical review matters.

If you are wondering whether the results apply to you specifically, that is an honest and reasonable question. Trial populations are carefully selected, and individual factors (starting weight, metabolic health, how nausea is tolerated during titration, how closely lifestyle changes are followed) all shape how much benefit a person sees. A prescriber's job, in part, is to have that conversation with you before treatment starts. You can read more about how the trial evidence connects to real-world prescribing on this overview of semaglutide weight-loss trial data.

What the 7.2mg approval added to the picture

In January 2026 the MHRA approved a higher 7.2mg maintenance dose of semaglutide for weight management, initially delivered as three 2.4mg pens per week, then, from April 2026, as a dedicated single-dose 7.2mg pen. Trial data for this dose reported around 20.7% average weight loss over 72 weeks, narrowing the gap with tirzepatide results seen in the SURMOUNT programme. The 7.2mg clinical trial evidence is worth reading if you are specifically researching the higher-dose option.

One thing worth knowing: the 7.2mg pen carries a BMI licence of 30 and above only, it is not licensed for the cardiovascular indication. The dose schedule still starts at 0.25mg and climbs through the standard titration steps; 7.2mg is the ceiling, reached gradually under prescriber guidance. Specific dose availability is confirmed during clinical assessment, not assumed in advance.

For context on how the Wegovy dose ladder is structured, the dose-order page walks through the full titration sequence. And if you are comparing the overall Wegovy evidence picture with what the wider Wegovy trial programme covers, that page brings the threads together.

From clinical trial to private prescription: what the evidence means for access

If you have spent time reading trial data and are now trying to work out what it means for actually starting treatment, that is a completely normal place to land. The evidence is compelling; the NHS pathway is real but restricted; and the private route exists precisely because licensed eligibility is broader than NHS commissioning criteria.

Semaglutide is only available on a private basis in the UK through a registered pharmacy, following a prescription from a qualified prescriber. There is no legal route to these medicines without that clinical step. At nume, a GPhC-registered Independent Prescriber personally reads every consultation (your answers go to a clinician, not through automated triage) and a decision is made the same day. Our pharmacy holds GPhC premises registration 9012878, verifiable on the regulator's own register.

Treatment pricing, what is included, and how the process works from consultation to delivery are all set out on the Wegovy access page. If you want a broader look at the options available, the weight-loss treatment overview covers both Wegovy and Mounjaro side by side. When you are ready to speak to our prescribers, the free consultation is the place to start.