Wegovy trial results: what the clinical evidence shows

Step 1: how the main STEP trial measured weight loss

The STEP programme was a series of phase-3 randomised controlled trials. STEP 1 recruited 1,961 adults with a BMI of 30 or above (or 27 or above with at least one weight-related condition) who did not have type 2 diabetes. Half received once-weekly semaglutide 2.4mg injections; the rest received a placebo. Both groups followed a reduced-calorie diet and increased their physical activity. After 68 weeks, average weight reduction in the semaglutide group was approximately 14.9%, against around 2.4% in the placebo group, a difference of roughly 12.5 percentage points, published in the New England Journal of Medicine. Around one in three participants lost more than 20% of their body weight. If you want to understand what those figures look like in practice, the Wegovy results page covers how outcomes vary across different patient groups and what the numbers mean in real-world terms. These are group averages from a controlled trial setting, not guarantees; individual results spread widely around the mean.

The dose used in STEP 1 was the 2.4mg weekly maintenance dose, reached gradually over about four months on a stepping schedule set by the prescriber. Early weeks at lower doses allow the body to adjust before reaching that level.

Step 2 and beyond: what the broader programme added

STEP 2 examined semaglutide in adults who also had type 2 diabetes, where average weight loss was around 9.6%, lower than STEP 1, which is consistent with what clinicians see across GLP-1 medicines in people with diabetes. STEP 3 combined the injection with intensive behavioural therapy and reported average losses above 16%, suggesting that structured lifestyle support amplifies the medicine's effect. STEP 4 tested what happens when treatment stops: participants who switched to placebo after 20 weeks on semaglutide regained most of the weight they had lost by week 68, while those who continued lost a further 7.9% on average. That finding matters. It tells you that for most people this is a long-term medicine rather than a short course. NICE's appraisal of semaglutide (TA875) drew on this programme when recommending it for use in specialist weight management services.

The 7.2mg evidence and where Wegovy's results stand today

The standard 2.4mg maintenance dose was the ceiling in the STEP programme, but in January 2026 the MHRA approved a 7.2mg dose of Wegovy, and in April 2026 approved a dedicated single-dose 7.2mg pen. Trial data for 7.2mg reported average weight loss of around 20.7% over 72 weeks, narrowing the gap with tirzepatide's published figures considerably. The SURMOUNT-5 head-to-head trial, published in the New England Journal of Medicine in 2025, compared tirzepatide directly with semaglutide 2.4mg (not 7.2mg) and found tirzepatide produced greater average weight reduction over 72 weeks. Whether the newer 7.2mg semaglutide dose changes that comparison is an active clinical conversation. Both medicines are licensed in the UK for weight management; which is the better fit is a clinical question, not a chart one.

If you want a closer look at how early results tend to build week by week, the six-week results page covers what participants typically experienced in the first month and a half of the STEP trials. For a broader picture of the medicine itself, the Wegovy overview covers licensing, eligibility and how it works. Context on cost, which is a practical question for many people, is covered on the weight-loss treatments page.

What the trial results mean for you as a patient

Trial averages tell you what happened across a group under controlled conditions. In practice, results depend on how the medicine fits your biology, whether you can tolerate and stay on the maintenance dose, and what lifestyle changes you make alongside it. The pen lives in the fridge (most people keep it in the door, next to everyday items) and it is injected once a week on the same day each week, so routine matters. Consistent use, protein-adequate eating and staying hydrated all contribute to how much of the trial-level benefit transfers to real life. Our prescribers at nume see this pattern regularly: people who engage with the medicine as part of a longer behavioural shift tend to track closer to the upper range of published outcomes.

These are prescription-only medicines, and a GPhC-registered Independent Prescriber reviews every consultation personally (not software) before anything is dispensed. If you are wondering how quickly effects tend to become noticeable, the one-week and two-week results pages explain what the trial data shows for those early time points. For the fuller timeline from starting dose to plateau, how long Wegovy takes to work pulls that together in one place. If you think Wegovy may be right for you, you can start your free consultation, reviewed the same day by one of our prescribers, with same-day dispatch if you are clinically suitable and order before noon.