How does Wegovy work for weight loss?

What is Wegovy actually doing inside your body?

GLP-1 (glucagon-like peptide-1) is a hormone your gut releases in response to food. Its job is to signal fullness, slow stomach emptying, and nudge the pancreas to release insulin when blood sugar rises. It dissipates quickly under normal circumstances, which is why hunger can return within a couple of hours of eating.

Semaglutide, the active ingredient in Wegovy, is a synthetic version of GLP-1 engineered to resist the enzyme that usually breaks the natural hormone down. A single weekly injection keeps GLP-1 receptor activity elevated for the full seven days. The practical effect: appetite signals quieten, meals feel satisfying earlier, and the drive to snack between them fades. None of this is willpower. It is biology.

The NHS medicines page for semaglutide describes this as working on areas of the brain that regulate appetite and food intake, which is an accurate summary of what the trial data shows. The signal reaches hypothalamic pathways associated with satiety, not just the gut, which is why many people report that food simply becomes less preoccupying. For a fuller picture of the semaglutide mechanism, our dedicated semaglutide mechanism page goes deeper.

Weight loss follows the calorie deficit that reduced appetite creates, compounded by steadier blood-sugar responses that blunt energy crashes and subsequent cravings. The medicine does not burn fat directly; it changes the conditions that make overeating likely.

Does Wegovy really work, and what do the trial numbers mean?

The headline figure from STEP 1, the pivotal phase 3 trial, is roughly 15% average body-weight reduction at the 2.4mg maintenance dose over 68 weeks. That was published in the New England Journal of Medicine and underpins the UK licence and the NICE recommendation (TA875). About one in three participants lost more than 20%. About one in twenty lost less than 5%.

Those numbers reflect averages from a clinical trial population. Individual results vary based on starting weight, dose tolerability, metabolic factors, and how closely people follow dietary guidance alongside the injection. Wegovy is licensed for use alongside a reduced-calorie diet and increased physical activity, the medicine supports those changes, it does not replace them.

For anyone wondering whether the results hold up in the real world, our page on Wegovy's effectiveness looks at what the evidence says beyond the headline trial figure. And for those curious about whether it is worth it for weight loss specifically, that page compares expectations against trial outcomes honestly.

A newer development worth knowing: the MHRA approved a 7.2mg maintenance dose in January 2026, and a dedicated single-dose 7.2mg pen was approved on 14 April 2026 for adults with a BMI of 30 or above. Early data suggests around 20.7% average weight loss over 72 weeks, narrowing the gap with tirzepatide. The titration schedule remains the same; you start at 0.25mg regardless of which maintenance dose you eventually reach.

How does the dosing schedule connect to how Wegovy works?

Wegovy starts at 0.25mg weekly and steps up, roughly every four weeks, through 0.5mg, 1.0mg and 1.7mg before reaching the 2.4mg maintenance dose. The lowest dose is not there to produce weight loss; it is there because GLP-1 receptor agonists cause nausea in many people when introduced abruptly at higher levels. Starting gently lets the gut adjust.

The titration process is decided by your prescriber, not by you. Staying at a given dose longer is sometimes clinically sensible; moving up faster is not. That is one reason prescription oversight matters throughout treatment, not just at the start. A prescriber who reviews your progress before each dose change is doing something substantive. Our guide to how to take Wegovy for weight loss covers the practical side of injections, injection sites and what to do if you miss a dose.

One practical routine note: the pen needs to be kept in the fridge, ideally somewhere easy to reach, many people keep it in the fridge door and inject on the same day each week, building the habit around something they already do. The Patient Information Leaflet specifies the exact window during which a pen can be kept at room temperature; the SmPC on the eMC carries the same detail for prescribers and patients who want the precise figures.

Who can access Wegovy, and is it available through the NHS?

Wegovy is licensed for adults with a BMI of 30 or above, or 27 to 29.9 where at least one weight-related condition is present, type 2 diabetes, high blood pressure, dyslipidaemia, sleep apnoea and cardiovascular disease are the usual examples. Lower BMI thresholds apply for some ethnic backgrounds under UK guidance. A BMI that meets those numbers does not guarantee a prescription; a prescriber assesses the full clinical picture.

On the NHS, NICE's recommendation (TA875) limits Wegovy to 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. Waiting lists through that route are commonly long. Private prescribing operates under the same licensed eligibility criteria but without the NHS service restrictions. If you want to understand what Wegovy costs privately, that page gives an honest picture of what the price includes and what to look out for.

Semaglutide is also available as a once-daily tablet (Wegovy in oral form) approved by the MHRA in June 2026 as the first oral GLP-1 medicine licensed for weight management in the UK. Our semaglutide options page explains the difference between injection and tablet, and the Wegovy treatment page covers what is currently available through nume. Check your eligibility by starting a free consultation, a GPhC-registered prescriber, not software, reviews it the same day.