What Wegovy study results tell us — and what they don't

What STEP 1 actually measured, and why 15% is a starting point, not the full picture

The STEP 1 trial enrolled 1,961 adults with a BMI of 30 or above, or 27 or above with at least one weight-related condition, none of whom had type 2 diabetes. Over 68 weeks, those randomised to semaglutide 2.4mg lost an average of 14.9% of body weight; the placebo group lost 2.4%. Headline averages, though, can flatten something important: the spread of individual results was wide. Around 69% of people on semaglutide lost at least 10% of their starting weight, and approximately 32% lost 20% or more. A meaningful minority lost less than 5%. That variation is worth sitting with. It is one reason why a prescriber assesses your full picture rather than simply pointing at a trial average and expecting it to apply to you directly.

There is a misconception worth addressing gently here: some people assume that because a trial reports a 15% average, they should see exactly that figure by week 68, and that anything less means the medicine has failed. Trial averages tell us about a population; they don't set a personal target. Factors including starting weight, how well the dose was tolerated, dietary changes, activity levels and individual biology all shape the result. Our page on slower-than-expected progress on Wegovy looks at this more practically.

All participants in STEP 1 also received counselling on reduced-calorie eating and increased physical activity. The medicine is licensed alongside those changes, not instead of them. The NHS medicines page for semaglutide reflects this framing clearly.

How the 7.2mg dose changed the picture

For several years, 2.4mg weekly was the highest available maintenance dose of Wegovy. That changed in early 2026. The MHRA approved a 7.2mg dose of semaglutide (Wegovy) in January 2026, and then on 14 April 2026 approved a dedicated single-dose 7.2mg pen, a pre-set, once-weekly injection with a built-in covered needle. Trials at this higher dose reported approximately 20.7% average weight loss over 72 weeks, a result that substantially narrows the gap between semaglutide and tirzepatide (Mounjaro) at its highest dose.

The 7.2mg pen is licensed for adults with a BMI of 30 or above. Starting dose remains 0.25mg, titrated upward by a prescriber roughly every four weeks; 7.2mg is the ceiling. Whether any individual reaches that dose depends on tolerance and clinical review at each stage. For anyone who found the standard 2.4mg maintenance dose effective but incomplete, the higher option is worth discussing with a prescriber. Our overview of Wegovy in the UK covers the full licensed picture, including how the two pen formats sit alongside each other.

It is also worth knowing that how long Wegovy takes to work is a separate question from peak efficacy, the first weeks look different to the longer-term picture, and managing that expectation from the start tends to help.

Early results, longer-term trends, and what happens between

Trial data is collected at specific endpoints (68 or 72 weeks is the usual mark for the STEP programme) but weight loss does not arrive uniformly across that period. Most people see relatively modest changes in the first few weeks as the dose builds and the body adjusts. The early weeks are largely about tolerability. Meaningful weight changes typically become clearer from around weeks six to twelve onward, with the steepest progress often seen in the middle portion of treatment.

Our pages on first-week results and six-week results set realistic benchmarks at those points, both drawn from the same trial evidence rather than anecdote. If you're curious about what the longer arc looks like beyond those early milestones, the broader Wegovy results page covers the full trajectory through to the trial endpoints.

One practical note on cost context: understanding what drives the price of a private semaglutide prescription is easier once you know what a full course of treatment involves clinically. Our Wegovy price guide walks through what legitimate private prescriptions include and what the market looks like following the Eli Lilly and Novo Nordisk pricing changes of 2025.

What trial evidence means for individual assessment

Clinical trial results establish that a medicine works at a population level under controlled conditions. They inform NICE's recommendations and the MHRA's licensing decisions. NICE's appraisal of semaglutide (TA875) concluded it is recommended within specialist weight management services for adults with a BMI of 35 or above and at least one weight-related condition, with ethnic-background BMI thresholds typically 2.5 kg/m² lower. The NHS route involves those criteria and waiting lists that can be long.

Private prescription is the alternative for people who don't meet the NHS thresholds or prefer not to wait, provided they meet the licensed eligibility criteria and are assessed as clinically suitable. At nume, every consultation is read by a GPhC-registered Independent Prescriber on the day it's submitted. No automated sign-offs. The prescriber weighs the trial evidence, your health history and your circumstances together. That is what translates a population average into an individual plan. If you'd like to talk through whether Wegovy is appropriate for you, our prescribers are the right starting point, start your free consultation here.