How long does a dose of semaglutide last in your body?

You've just injected, here's what's happening over the next seven days

Picture the hours immediately after your injection. Semaglutide is absorbed gradually from the subcutaneous tissue, reaching peak plasma concentration around one to three days after the dose. That slow rise is intentional: a sharper spike would mean a rougher ride of nausea and then a steep drop-off in appetite suppression before your next injection. Instead, the medicine climbs to its peak, plateaus, and then declines steadily so that by day seven (when you inject again) there is still a measurable level circulating. The biological half-life of semaglutide sits at roughly 165 to 184 hours, which works out to just under seven days.

This pharmacokinetic profile is one reason the dosing schedule for semaglutide is set weekly rather than daily. The medicine does not need topping up every morning; it sustains its action across the full interval. That said, "last seven days" does not mean a flat, unchanging effect throughout. Appetite suppression, fullness signals and gastric emptying all tend to be strongest in the two to four days after a dose and soften slightly towards day six or seven. Some people notice this rhythm once they are on a stable dose and find that days six and seven feel slightly different from days two and three. That is normal physiology, not a sign something has gone wrong.

The NHS semaglutide information page confirms the once-weekly schedule and notes that the injection can be given on any day of the week, at any time of day, as long as you keep to the same day each week.

Why steady state (not the first injection) is when full effects kick in

A common source of confusion is expecting the first pen to deliver the same results as the fifth. It does not, and the reason is straightforward. With any medicine that is dosed repeatedly, each new dose adds to the level still present from the previous one. Over four to five consecutive weekly doses, circulating semaglutide accumulates until it reaches what clinicians call steady state, the point at which the amount added each week equals the amount cleared.

At steady state, the medicine's effect on appetite and weight is at its full potential for that dose level. Before that point, levels are still building. This is part of why the titration schedule starts low and steps up gradually: the body is adjusting both to the tolerability of each dose and to the accumulating pharmacological effect. Expecting dramatic appetite change in week one is the wrong frame; the more useful expectation is consistent, progressive effect that deepens over the first month or two.

For a thorough look at how dose steps work across the titration schedule, this page on semaglutide dosing covers each stage in detail. If you are curious specifically about whether one strength has a meaningfully different duration, the answer is that the half-life itself does not change with dose, a higher-strength pen lasts the same seven days; what changes is the peak concentration and overall drug exposure.

What happens to duration if you miss a dose or stop treatment

Life gets in the way sometimes. If a dose is delayed or skipped, the seven-day half-life means you have a practical grace period. UK guidance (reflected in the patient information leaflet) states that a missed dose can be taken up to five days after the scheduled day. If more than five days have passed, skip that dose and resume on the next scheduled day. Do not take two doses in one week to compensate. Any questions about a specific missed dose should go to your prescriber or the Patient Information Leaflet; this page is here to explain the biology, not to replace clinical advice.

Stopping treatment is a different question from missing a single dose. After the last injection, semaglutide does not vanish overnight. With a half-life of roughly seven days, it takes five or more half-lives (that is, five weeks or more) before the drug is substantially cleared. During that period, some appetite-suppressing effect persists and then gradually fades. What happens after your last dose of semaglutide is covered in more depth separately, including what to expect as clearance progresses. Separately, for anyone wondering about a specific pen strength, the duration profile of the 5mg dose follows the same seven-day half-life principle.

If weight management treatment is something you are actively considering, a free consultation with our prescribers is the starting point, a real clinician reviews your details the same day, and there are no automated decisions involved.

The oral Wegovy tablet: does duration change when you swallow it instead of inject it?

As of summer 2026, semaglutide is also available as a once-daily tablet (Wegovy tablets) approved by the MHRA on 11 June 2026 as the first oral GLP-1 medicine licensed in the UK for weight management. The pharmacokinetics shift considerably. Oral semaglutide is absorbed through the stomach wall with the help of an absorption enhancer, and because absorption is less efficient and more variable than subcutaneous injection, it is taken every day rather than every week to maintain consistent levels.

The practical result is that a single tablet of oral semaglutide does not last seven days; it is designed to be replenished daily. The effective duration per dose is closer to 24 hours, which is why missing even one day matters more with the tablet than a one-day slip with the injection. Taking it correctly (first thing in the morning, on an empty stomach, with a small amount of plain water, and then waiting at least 30 minutes before food or other medicines) is particularly important for consistent absorption. What happens around your last dose of Wegovy applies to both formulations, though the clearance timeline differs slightly between the injection and the tablet given the different dosing rhythm. If cost is on your mind as you weigh up your options, this honest breakdown of Wegovy pricing in the UK sets out what to expect from private treatment.