Redefine 1 semaglutide weight loss percentage: reading the trial results honestly

What REDEFINE 1 actually measured, and why the percentage matters

REDEFINE 1 was a phase 3 randomised controlled trial evaluating oral semaglutide at a 50mg maintenance dose alongside lifestyle counselling in adults with a BMI of 30 or above, or 27 and above with at least one weight-related condition. The trial ran for 68 weeks and compared semaglutide with placebo. The primary endpoint was percentage change in body weight from baseline.

The intention-to-treat result of approximately 15.1% sits in a specific analytical frame: it divides the outcome across every participant randomised, including those who stopped early. This is the methodologically conservative choice, and it is the right number to quote when discussing what an unselected group of people might achieve. Among those who completed the full protocol, average reductions were higher, a distinction worth understanding if you are trying to reconcile different figures you may have seen reported.

One misconception worth setting aside gently: these percentages do not describe a ceiling. They describe a distribution. Some participants in REDEFINE 1 lost considerably more; others less. Individual biology, starting weight, diet and activity all shift the result. A trial average is a useful anchor, not a personal prediction. Our page on how Wegovy's weight loss percentages are calculated unpacks this further if you want the statistical detail.

The REDEFINE 1 findings were an important step in demonstrating that meaningful weight loss is achievable through an oral semaglutide formulation, ahead of the UK regulatory process that would eventually licence Wegovy tablets separately from the weekly injection.

How REDEFINE 1 compares with the injection trials

Wegovy as a weekly subcutaneous injection was evaluated primarily in the STEP programme. The STEP 1 trial reported an average weight reduction of around 15% at 68 weeks with the 2.4mg injection, a result broadly in the same territory as REDEFINE 1's oral 50mg figure, though direct comparison between trials is complicated by differences in populations, primary endpoints and adherence definitions.

The picture shifted further with the approval of the 7.2mg weekly injection. Trials at that higher dose reported approximately 20.7% average weight loss over 72 weeks, narrowing the gap with tirzepatide's results. Context matters: the approved UK licence for Wegovy injection covers the 7.2mg dose only for adults with a BMI of 30 or above, not for lower BMI thresholds.

For the oral tablet specifically, OASIS 4 (the trial that underpinned the MHRA approval of Wegovy tablets on 11 June 2026) reported around 13.6% average weight loss at the intention-to-treat level over 64 weeks, rising to approximately 16.6% among participants who adhered fully. REDEFINE 1's 15.1% at 68 weeks sits above the OASIS 4 intention-to-treat figure, likely reflecting the higher 50mg dose tested rather than any methodological gap. You can read more about how semaglutide works and why dose influences outcome.

For anyone weighing up cost alongside efficacy data, our Wegovy price comparison sets out what private treatment typically costs in the UK and what a legitimate price should include.

What these percentages mean for eligibility and realistic expectations

NICE recommended injectable semaglutide (Wegovy) under technology appraisal TA875 for adults meeting BMI and comorbidity criteria, within specialist weight management services and for a maximum of two years on the NHS. The Wegovy tablet received MHRA approval in June 2026 but has not yet been through a NICE appraisal, so it is currently available only as a private prescription.

Private eligibility for semaglutide broadly follows the licensed criteria: a BMI of 30 or above, or 27 to 29.9 with at least one weight-related condition such as high blood pressure, high cholesterol or type 2 diabetes. Lower thresholds apply for some ethnic backgrounds under UK guidance. BMI alone does not determine suitability; a prescriber looks at medical history, existing medications and overall clinical picture before issuing any prescription.

The REDEFINE 1 percentage is a population average from a controlled research setting. Real-world outcomes depend on how consistently treatment is taken, what happens at each dose step, and how well lifestyle changes are maintained alongside it. The interaction between semaglutide and body composition (including effects on lean mass) is a related question our page on semaglutide and lean mass percentage addresses in full.

If you have questions about inflammation markers or metabolic changes during treatment, there is also detail available on semaglutide's effect on hsCRP, a cardiovascular risk marker that has shown reductions in trial data alongside weight loss.

Understanding the evidence is the first step. The next is a clinical assessment with a qualified prescriber. Check your eligibility with nume, a GPhC-registered prescriber reviews every consultation personally, the same day.