When is semaglutide at its peak — and what does that mean for you?

What does 'peak' actually mean for a weekly injection?

When people ask when semaglutide is at its peak, they are usually asking one of two distinct questions: when is the medicine at its highest concentration in my body this week, and when will I feel the strongest effects overall? The answers are quite different, and it helps to hold them apart.

After a subcutaneous injection, semaglutide is absorbed slowly from the tissue beneath the skin. Blood concentration climbs over roughly one to three days, reaching its highest point somewhere in that window, a pattern that is worth understanding in detail if you want to make sense of your weekly rhythm. This is described in the pharmacokinetics data for Wegovy and is consistent with NHS guidance on semaglutide. Appetite reduction and a feeling of fullness often track this rise, which is why some people notice the days immediately after their injection feel different from days six or seven.

Because the half-life of semaglutide is approximately one week, concentrations do not fall to zero before the next dose. Each weekly injection adds to what remains. Over four to five weeks of consistent dosing, levels stabilise into what pharmacologists call steady state, a more consistent background level. That background is what drives the sustained appetite change most patients describe.

Practical note: if you keep your pen in the fridge door and inject on the same day each week, the rhythm becomes predictable. Timing your injection day is worth a conversation with your prescriber; there is useful detail on choosing when to take semaglutide that covers morning versus evening and other practical factors.

When do weight-loss results peak during a course of treatment?

This is where the conversation about when Wegovy is at its peak, including which day of the weekly cycle that tends to correspond to, gets more clinically meaningful. Weight loss on semaglutide does not arrive in the first weeks. The starting dose (0.25 mg) is a tolerability step; its job is to acclimatise your system to the medicine, not to produce rapid results. Dose titration typically proceeds over several months before reaching the full maintenance level.

The STEP 1 trial, published in the New England Journal of Medicine, followed adults on semaglutide 2.4 mg for 68 weeks alongside lifestyle changes. Average body-weight reduction was around 15%. That figure came after sustained treatment, not from early weeks. Weight loss in the trial was progressive, with the steepest changes occurring in the mid-treatment period and then levelling as participants approached their personal plateau.

The approved higher dose of 7.2 mg (the MHRA approved a dedicated single-dose 7.2 mg pen on 14 April 2026) has reported average losses of around 20.7% over 72 weeks. Again, those results reflect months at the maintenance dose. The peak of clinical effect, meaning the point at which semaglutide's impact on weight is greatest, is therefore best understood as a range spanning roughly weeks 36 to 72, not a single moment.

If you are comparing Wegovy with tirzepatide (Mounjaro), our weight-loss treatments overview sets out what the evidence currently shows, including the head-to-head SURMOUNT-5 data.

Does the peak change if a dose is missed or delayed?

Yes, modestly. Missing a dose interrupts the weekly rhythm and means the body's semaglutide level dips further than it would with consistent dosing. Many people who miss a dose report that hunger returns more noticeably around days five to seven, which reflects those falling concentrations rather than the medicine stopping work.

The Patient Information Leaflet and your prescriber's guidance should be your first reference if a dose is missed. General advice typically allows for taking a missed dose within a few days, provided the next scheduled dose is not too close, but the specific guidance is in the leaflet, and the right call depends on your individual situation. This page explains the pharmacology; your prescriber advises on your dose schedule.

Questions about timing, missed doses and what to expect in week one versus week twelve, including when semaglutide peaks during early treatment, come up frequently. Our frequently asked questions page covers a range of common practical queries, and our clinical team is reachable seven days a week for aftercare support.

What does steady state feel like, and how will you know you're there?

Steady state is not a dramatic threshold. Most people describe a gradual shift: appetite that once fluctuated through the week becomes more consistently lower, and the pronounced post-injection awareness of days two and three softens. This usually takes four to five weeks of injections at a given dose.

When a dose is increased, the cycle essentially resets. Concentration climbs to a new, higher steady state over another four to five weeks. Side effects, particularly the gastrointestinal ones (nausea, loose stools, reflux) tend to be most noticeable in the first one to two weeks at each new dose level, then ease for most people. The NHS semaglutide medicine page lists the full side-effect profile. Any side effect that is severe or persistent should be discussed with a clinician rather than waited out.

For a broader picture of how Wegovy works and what to expect across a full course of treatment, the Wegovy guide on this site pulls together the licensed doses, eligibility and the clinical evidence in one place. And if you are ready to find out whether treatment is suitable for you, check your eligibility with our prescribers, consultations are free, and every assessment is read by a real clinician the same day.