Wegovy's Peak Concentration and Half-Life Explained

What the trial evidence says about how semaglutide builds up

The pharmacokinetic data for subcutaneous semaglutide comes partly from the large STEP programme trials, where participants received once-weekly injections over 68 weeks. The STEP 1 trial, published in the New England Journal of Medicine, reported an average weight reduction of around 15% over 68 weeks at the 2.4mg maintenance dose. Those results depend entirely on a stable, sustained plasma level of semaglutide, and that stability flows from the half-life.

Semaglutide is bound tightly to albumin in the bloodstream, which slows its clearance significantly. The result is a half-life of roughly seven days. After a single injection, peak concentration arrives within one to three days. From that peak, levels decline slowly, so by the time the next weekly injection is due, circulating semaglutide is lower but far from absent.

This pattern has a practical consequence: the medicine accumulates over several weeks of regular dosing. Steady-state plasma concentrations (the point where the amount entering the body each week matches the amount leaving) are typically reached after four to five weeks of consistent dosing. That is one reason the clinical benefits of Wegovy continue to deepen through the early months of treatment rather than plateauing immediately.

For a fuller picture of how these numbers compare across doses and time points, the semaglutide half-life chart on this site sets it out clearly.

Why the half-life shapes the dose-escalation schedule

The fact that semaglutide lingers for weeks is precisely why the titration schedule moves in four-week steps rather than one-week ones. Each new dose needs roughly four to five half-lives (that is, four to five weeks) before it reaches its own steady-state level. Rushing the escalation would mean the body is absorbing increasing concentrations before the previous dose has settled, which raises the risk of gastrointestinal side effects.

The Wegovy injection schedule begins at 0.25mg and progresses through 0.5mg, 1.0mg, and 1.7mg before reaching the standard 2.4mg maintenance dose, each step held for at least a month. The same logic applies to the newer 7.2mg maximum dose approved by the MHRA in January 2026: it is reached by the same gradual escalation, with the prescriber judging when each step is appropriate.

This is also why missing a dose matters less than you might expect on some medicines, but still matters here. If a weekly injection is delayed by a day or two, plasma levels dip somewhat but do not collapse entirely. If a dose is missed by more than a few days, the Patient Information Leaflet and your prescriber's guidance should be followed, not assumptions based on the half-life alone.

Questions about how the titration compares to the oral route are worth exploring via the semaglutide peak concentration detail page.

How long semaglutide takes to clear after stopping

This is the question our prescribers hear regularly, and it matters for specific situations including pregnancy planning, switching treatments, and surgical procedures. The general answer, based on the pharmacokinetics published in the Wegovy SmPC and summarised on the NHS semaglutide medicines page: with a half-life of approximately one week, around five weeks are needed for semaglutide to fall to negligible levels after the final injection.

The MHRA advises using effective contraception while on GLP-1 medicines and for a wash-out period before trying to conceive. The specific recommended interval for semaglutide should be confirmed with your prescriber. If you're planning surgery, the anaesthetist needs to know you are taking a GLP-1 medicine, because gastric-emptying effects can persist for several weeks after the last dose.

One detail worth flagging: for patients who have been on treatment a long time, body-weight changes during treatment can affect how the medicine distributes and is metabolised to some degree, another reason the clearance timeline is something to discuss personally rather than assume. If you're thinking about stopping, that conversation belongs with your prescriber, not a forum.

If you're weighing up how the half-life compares to other semaglutide formats, the semaglutide half-life overview covers the injection and oral routes side by side. And for people thinking about how long treatment might continue overall, the question of whether Wegovy is a lifelong medicine is answered in full separately.

Timing, missed doses and real-world patterns

In clinical practice, the once-weekly schedule turns out to be one of the things patients adapt to quickly. The long half-life gives a small buffer, if your delivery is slightly delayed, or a busy week means your injection day shifts by 24 hours, the pharmacokinetics mean blood levels don't plummet overnight. That said, a consistent weekly day is still the recommendation, because it keeps the curve of rising and falling levels predictable and the GI side-effect pattern manageable.

If you order before noon Monday to Friday and your prescription is approved that same day, treatment arrives the next working day. Worth thinking about if you're mid-pack and planning ahead around bank holidays or travel. Stock up a week early if a holiday is coming, running out is the main avoidable disruption to steady-state levels.

Cost is a separate consideration from pharmacokinetics, but worth understanding. The Wegovy cost context page explains the UK private pricing landscape honestly, including what a legitimate prescription price actually covers. At nume, one transparent price includes the consultation, the prescription, the medicine and free next-working-day delivery, no separate fees stacked on at checkout.

If you'd like a prescriber to assess whether Wegovy is clinically suitable for you, you can start your free consultation here. A GPhC-registered Independent Prescriber reads every consultation personally, the same day.