How Long Until Wegovy Leaves Your System — and Why It Matters

Step 1, The week after your last injection: concentration starts to fall

Semaglutide reaches its peak concentration roughly one to three days after a weekly subcutaneous injection, then begins to decline. Its half-life sits at approximately one week. That means the week after your final dose, plasma levels have already halved, but they are far from negligible. Appetite suppression, slowed gastric emptying and the nausea that some people experience can all persist at this stage, because meaningful amounts of the medicine are still circulating. The precise peak and subsequent drop vary slightly depending on injection site, body composition and the dose you were taking at the time you stopped. For most people at the 2.4mg maintenance dose, week one post-injection feels not dramatically different from a normal dosing week, the drug is still working.

This pharmacokinetic profile is why semaglutide is dosed weekly rather than daily; the slow absorption and long half-life create a stable plateau during treatment. The flip side is that it does not switch off quickly. If you are stopping for a medical reason, tell your prescriber rather than simply missing a dose.

Step 2, Weeks two to four: the gradual decline and appetite returning

Each passing week removes roughly half of whatever concentration remained. By the end of week two, levels are at around a quarter of where they were on treatment; by week three, an eighth. In practice, this is when many people first notice appetite creeping back. Portion sizes that felt perfectly comfortable on treatment can start to feel less filling. Energy regulation shifts. Some people also notice that digestive rhythms change again as gastric emptying speeds up toward normal. This is not a sign that something has gone wrong, it is the expected pharmacology.

The way semaglutide accumulates during treatment is the mirror image of this process: steady build-up over several weeks means steady decline over several weeks. For anyone managing other medicines during this period, it is worth flagging the washout to a GP or pharmacist, since drug absorption can normalise as gastric emptying returns to its baseline rate. You can read more about how semaglutide works on our medicines overview page.

Step 3 (Week five and beyond: clinically negligible levels

By the end of five weeks) approximately five half-lives, semaglutide concentrations are at roughly 3% of steady-state levels. Clinically, this is considered the functional clearance window, and our guide on how long semaglutide takes to clear your system explains what that window looks like in practice. The NHS guidance on semaglutide notes that the medicine stays in the system for a number of weeks after stopping, and prescriber-level references such as the BNF reflect the approximately five-week washout period when advising on matters like conception planning.

That five-week figure matters in several practical situations. If you are planning surgery, anaesthetists may want to know when you last took a GLP-1 medicine because of its effect on gastric emptying, NHS England advises telling your whole healthcare team, including the anaesthetist, before any procedure. If you are planning to conceive, MHRA guidance recommends a washout period before trying, because the medicine is not recommended in pregnancy. And for those considering switching to a different weight-management approach, it helps to know the playing field does not level immediately after the last injection.

It is also worth noting that clearance does not mean instant weight return. Biological factors that the medicine was moderating (insulin sensitivity, appetite-hormone signalling) do not revert overnight either. Wegovy's licensed use is intended alongside sustained lifestyle changes precisely because the medicine works best as part of a longer-term approach.

What the washout window means for oral semaglutide and contraception

The same underlying pharmacology applies to the Wegovy tablet, approved by the MHRA on 11 June 2026 as the first oral GLP-1 medicine licensed in the UK for weight management. Oral semaglutide has comparable systemic exposure once absorbed, so the washout conversation is similar even without a weekly injection to track. The mechanism that keeps semaglutide active between weekly doses (binding to albumin, protecting it from breakdown) applies equally to the tablet form.

On contraception: NHS England guidance specifically notes that GLP-1 medicines slow gastric emptying, which may reduce absorption of oral contraceptive pills. During the washout period after stopping, this effect diminishes gradually rather than stopping sharply. If you switched to a non-oral contraceptive method while on treatment, discuss with your GP when it is appropriate to return to an oral method. This is one of the questions our prescribers hear regularly; if you have questions about stopping or switching treatment, the general FAQs cover many of the common ones, and our team is available seven days a week via contact. For a broader look at weight-loss treatment options once a washout is complete, our overview page is a useful starting point. When you are ready to explore what is clinically right for you, start your free consultation with our prescribers.