Wegovy statistics: what the clinical trial numbers actually show

Step 1: the core STEP 1 results and what 15% means in practice

The STEP 1 trial, published in the New England Journal of Medicine in 2021, is the most cited source for Wegovy weight loss statistics. It randomised 1,961 adults with obesity or overweight plus at least one weight-related condition over 68 weeks. Participants on semaglutide 2.4mg lost an average of 14.9% of body weight; the placebo group lost 2.4%.

Averages can obscure as much as they reveal. Within the semaglutide group, around 69% of participants lost at least 10% of starting body weight, and approximately 32% lost 20% or more. At the other end, a meaningful minority lost considerably less. If you want a fuller breakdown of how those figures are distributed, our page on Wegovy stats pulls the numbers together in one place. That spread reflects the biological reality: response to GLP-1 medicines differs between individuals, shaped by genetics, metabolic history, diet, activity and adherence to the full 68-week programme.

All participants also received lifestyle counselling throughout the trial. The weight loss figure is not semaglutide in isolation; it is semaglutide as part of a structured programme. Our overview of Wegovy as a treatment sets out what that wraparound support looks like in practice.

Step 2: what the newer 7.2mg data adds to the picture

The standard 2.4mg maintenance dose was approved in the UK years before the STEP 1 paper. More recently, the MHRA approved a 7.2mg maintenance dose on 12 January 2026, followed by a dedicated single-dose 7.2mg pen on 14 April 2026. Clinical trial data for 7.2mg reported an average weight loss of around 20.7% over 72 weeks, substantially above the 15% figure that most people associate with Wegovy.

That closes part of the gap with tirzepatide (Mounjaro), which produced around 20–21% average weight loss in the SURMOUNT-1 trial at its highest dose. The two medicines work differently at a receptor level: semaglutide acts on a single GLP-1 pathway, while tirzepatide targets both GLP-1 and GIP receptors. You can read more about how the clinical evidence compares across the full range of weight-loss treatment options we offer.

One practical point worth knowing: the 7.2mg dose is only licensed for adults with a BMI of 30 or above. It is not currently approved for the cardiovascular indication. A prescriber decides whether the higher dose is appropriate at each stage of treatment.

Step 3: eligibility thresholds and how statistics translate to individual suitability

NICE's appraisal of semaglutide, TA875, recommends its use within specialist NHS weight management services for adults with a BMI of 35 or above (or 30–34.9 where specialist-referral criteria are met) and at least one weight-related comorbidity, for a maximum of two years. Lower BMI thresholds apply for South Asian, Chinese, Middle Eastern, Black African or African-Caribbean backgrounds under UK guidance, typically 2.5 kg/m² below the standard figures.

Private prescribing follows the licensed SmPC criteria: adults aged 18 or over with a BMI of 30 or above, or 27–29.9 with at least one weight-related condition such as hypertension, high cholesterol or obstructive sleep apnoea. BMI alone is never the whole picture; a prescriber weighs the full medical history. If you are considering private treatment, our clinical team reviews every consultation personally.

One figure from the STEP programme that matters for eligibility discussions: STEP 1 recruited participants without type 2 diabetes. Separate trials in people with type 2 diabetes showed smaller average losses, partly because diabetes itself affects the degree of glycaemic-driven appetite. The headline 15% figure applies to adults with obesity or overweight without diabetes. It is worth flagging this when reading any published Wegovy statistic.

Step 4: cost, access and what treatment actually involves

Statistics from trials tell you about the medicine. They say nothing about what the day-to-day experience looks like. Most people start at 0.25mg, titrating roughly every four weeks up to the 2.4mg maintenance dose, under prescriber guidance. Side effects are predominantly gastrointestinal (nausea, loose stools, reflux) most common after a dose increase and typically settling within a couple of weeks. The NHS patient information for semaglutide covers the full side-effect profile clearly.

Treatment arrives as a pre-filled pen. Through nume, once a consultation is clinically approved, the pen is dispatched the same day and delivered by DPD the next working day in plain, unbranded packaging, you get a tracking notification so there is no guessing when it will arrive. If you want to understand how Wegovy is priced privately, that page sets out what a legitimate price covers and what market-context figures look like since the 2025 price changes. There are no subscription commitments; every repeat order is reviewed clinically before dispatch.

For anyone taking other medicines alongside Wegovy, interactions are worth exploring: the question of taking Wegovy with statins, for instance, comes up regularly in our consultations and has a factual answer worth reading before you ask. If you are on a course of antibiotics, our guidance on Wegovy and antibiotics explains what the evidence says and what to discuss with your prescriber. Gut changes on GLP-1 treatment also affect how some people respond to other supplements, which is one reason the topic of probiotics alongside Wegovy attracts genuine clinical interest.

The numbers from STEP 1 and the newer 7.2mg data are genuine and meaningful. They are also population averages from controlled trials, not predictions for any one person. The consultation exists precisely to translate a statistic into an individual clinical assessment.