How long semaglutide stays in your system after the last dose

The five weeks after your last injection, week by week

Picture your last Wegovy pen sitting in the sharps bin. The injection is done, but semaglutide doesn't simply switch off. Its half-life of around seven days means that one week after your final dose, roughly half the active drug remains in circulation. A fortnight out, you're down to about a quarter. By the end of week five, you're somewhere below 5% of the original concentration, which is the pharmacological threshold most clinicians treat as effective clearance.

In practice, that means the five-week window is the figure most often cited for planning purposes: surgery teams, fertility specialists and prescribers working through contraception choices all tend to use it as a reference point. The duration of a single semaglutide dose gives more detail on the weekly pharmacokinetics if you want to follow the numbers closely.

One thing worth knowing: clearance is not the same as the effects stopping. Appetite reduction and, for some people, nausea can taper gradually over the same five-week period rather than vanishing on day one. That slow fade is the same property that makes once-weekly dosing work in the first place. If you are curious about how long 0.5 Wegovy stays in your system at the starting dose, that page walks through the clearance curve specific to that stage. If you are curious about the full-strength maintenance stage, you can read about how long Wegovy 2.4mg stays in your system to see how the clearance curve plays out at that dose. The NHS semaglutide medicines page is a reliable place to read about how the medicine behaves in plain language.

Stopping before surgery, what your prescriber and anaesthetist need to know

This is the question our clinical team fields most often around the clearance topic. GLP-1 medicines slow gastric emptying, and that slowing doesn't disappear the moment you miss a dose. NHS England guidance states clearly that anyone taking a weight-management injection should inform their healthcare team, including the anaesthetist, before any surgical procedure. The concern is aspiration risk during anaesthesia: a stomach that empties more slowly than usual may retain contents even after a standard fasting period.

Surgical teams vary in exactly how long they ask patients to stop beforehand (some ask for one week, others for longer) so the conversation with the anaesthetist is essential rather than optional. If you want to understand how long 1mg Wegovy stays in your system, that page breaks it down at that specific dose level. The short version: five weeks of clearance time is a sensible planning horizon, but your surgical team sets the actual window for you.

It's also worth being honest with your prescriber if you've been tempted to stop quietly rather than flag it. Stopping without a plan isn't inherently dangerous, but restarting later often requires a clinical review and potentially returning to a lower dose, knowing that upfront saves a lot of frustration.

Contraception, pregnancy and the clearance window

For women of childbearing age, the five-week figure carries particular weight. Semaglutide is not recommended during pregnancy, whilst breastfeeding, or for anyone actively trying to conceive. The NHS England weight-management injections guidance advises using contraception throughout treatment and for a period after stopping, the washout period before trying to conceive should be agreed with a prescriber, with the five-week clearance window as the starting point of that conversation.

There's also a practical point specific to tirzepatide (Mounjaro) rather than semaglutide, but worth noting here for contrast: tirzepatide slows gastric emptying enough to reduce oral contraceptive pill absorption in the early weeks of treatment, so additional contraception is recommended during dose increases. NHS evidence for the same effect with semaglutide is less established, but the general advice remains to keep contraception in place while the medicine is active and during clearance. Your dose stage can affect the specifics, which is another reason prescriber guidance matters here rather than a general rule.

If you have questions about timing around a planned pregnancy, the right route is a conversation with a prescriber rather than working from a general article, the five-week figure is a guide, not a prescription.

What happens to weight and appetite during clearance

Being honest: many people feel some return of appetite during the five-week clearance window, and for some it's sharper than they expected. That's not a sign something went wrong. The appetite suppression that semaglutide produces is pharmacological; as levels fall, hunger signals that the medicine was dampening start to resurface. Weight regain is common after stopping GLP-1 treatment, clinical trial follow-up data show most people regain a significant proportion of lost weight within a year of stopping, which is why the decision to pause or stop is worth discussing properly with a prescriber rather than making unilaterally.

If you're exploring treatment options or thinking about what the wider landscape of weight-loss treatment looks like, that's a useful place to start. And if the reason you're looking into clearance is that you're thinking about switching treatment or restarting at a different dose, the free consultation with our prescribers is the right next step, they can review where you are now and advise on timing and the most appropriate path forward.