How long after a Wegovy shot does it work?

The day after your first injection: what you may (and may not) feel

Picture this: you've done your first Wegovy injection on a Sunday evening, and by Monday you're quietly watching your lunch plate, waiting for something dramatic to happen. For most people, it doesn't, at least not yet. Semaglutide is a GLP-1 receptor agonist: it mimics a gut hormone that signals fullness to the brain and slows how quickly your stomach empties. Those signals start the moment the medicine is absorbed, and plasma concentrations do peak within roughly one to two days of each injection.

What that means in practice varies enormously. Some people report a noticeably smaller appetite within 48 hours of their first pen. Others feel little different for two to three weeks. Neither experience is wrong. The starting dose (0.25 mg) is there to let your body adjust, not to produce maximum effect. Nausea, the most commonly reported early side effect, tends to land in this first window too, often peaking a day or two after the injection before settling. A practical habit worth building early: weigh yourself on the same morning each week, just after waking and before eating, and note it down. One data point tells you nothing; a six-week line tells you a great deal.

The question of when Wegovy starts working is partly about pharmacology and partly about what "working" means to you. Appetite change often comes first; the scales follow later.

Weeks four to sixteen: where steady-state changes things

After four to five weeks of weekly injections, semaglutide reaches what pharmacologists call steady state, the point at which each new dose replenishes a stable reservoir rather than building from scratch. This is when the medicine's effects become more consistent day to day, rather than cycling between peak and trough each week.

The dose-escalation schedule matters here. The standard Wegovy pathway moves from 0.25 mg to 0.5 mg, then 1.0 mg, 1.7 mg, and finally 2.4 mg, each step roughly four weeks apart, prescribed by your clinician. That means the majority of people are still titrating for the first four months. Weight loss during this phase is real but often modest; the more substantial changes tend to follow once the maintenance dose is reached and sustained.

People sometimes worry that slow early progress means the medicine isn't working for them. In most cases it simply means the body is still adjusting. How long Wegovy takes to work depends on which dose you're currently on, and that's a conversation worth having with your prescriber rather than drawing conclusions at week three. If you're weighing up costs alongside timelines, our Wegovy price comparison covers what private treatment typically involves in the UK.

Months three to eighteen: where the trial data actually lives

The STEP 1 trial (the pivotal phase-3 study, conducted over 68 weeks) found an average body-weight reduction of around 15% among adults taking semaglutide 2.4 mg alongside lifestyle changes, compared with about 2.4% for placebo. The full trial paper is published in the New England Journal of Medicine. That average conceals a wide spread: some participants lost considerably more, others less. The weight-loss curve in the trial was not a straight line, it steepened after the maintenance dose was reached and began to plateau around the 60-week mark.

This is the honest picture most people don't see in a headline: Wegovy's results are cumulative and slow-building, not front-loaded. The shot you give yourself this week is doing work that shows up on the scales over the following months. Consistency with weekly injections, the lifestyle changes your prescriber recommends, and enough time on the maintenance dose are the three things that shape your outcome. The duration of each shot's active effect is also worth understanding, semaglutide's half-life means it is still working a full week after injection, which is why weekly dosing sustains the effect rather than leaving gaps.

According to the NHS medicines page for semaglutide, treatment is typically reviewed if less than 5% weight loss is achieved after six months at the maintenance dose. That threshold is a clinical benchmark, not a verdict, it's one of the things a prescriber considers in ongoing reviews.

What slows results down, and when to raise it with your prescriber

Several things can make the timeline feel longer than the trial average suggests. Spending more weeks on lower doses (because of tolerability, or missed injections) delays reaching steady state at the maintenance level. Significant gastrointestinal side effects (nausea in particular) can temporarily reduce appetite in ways that feel like the medicine working, then settle, creating an impression of early success followed by a plateau. And individual biology genuinely varies: semaglutide's effects on appetite and weight are meaningful for most people but are not identical for everyone.

The places to direct these questions are your prescriber and the patient information leaflet that comes with every pen. If you're considering starting treatment and want a clear-eyed conversation about what to expect, getting Wegovy through a regulated online clinic begins with exactly that kind of clinical assessment. At nume, a GPhC-registered Independent Prescriber reads your consultation personally, your notes go to a clinician, not software. You can read more about how the clinical team is structured on our prescribers page.

If you have questions that aren't covered here, our FAQs address many of the practical details. And when you're ready to take the next step, you can start your free consultation, reviewed the same day, dispatched the same day if clinically suitable.