How soon does Wegovy start working — and what does 'working' actually mean?

You've just had your first injection. Here's what's happening right now.

Picture the scene: you've done your first 0.25 mg injection on a Sunday evening, put the pen back in the fridge, and you're wondering when anything is going to happen. The honest answer is that something probably already is, you just can't see it yet.

Semaglutide is a GLP-1 receptor agonist. It mimics a gut hormone that signals fullness to the brain, slows the speed at which your stomach empties, and reduces the intensity of hunger between meals. These processes begin after the first dose, but they are subtle at this stage. Most people report noticing food feels less urgent, meals feel satisfying sooner, and the pull towards snacking eases. That shift can arrive anywhere between day three and week three, and if you want to understand how soon Wegovy starts to work in more detail, our dedicated guide walks through exactly what to expect and when. For a deeper look at the mechanism behind this, our guide on how Wegovy works covers the pharmacology in plain terms.

What you will not see at this point is dramatic weight loss. The 0.25 mg starting dose is deliberately low, its job is to let your body adjust, not to maximise effect. Weight change at this stage is typically modest, and that is exactly as intended. Patience here is not passive; it is part of the clinical design.

Weeks four to twelve: when the scales start to reflect what your appetite already knows

By the time your prescriber moves you up from 0.25 mg to 0.5 mg (usually around week five), many people are already eating noticeably less without feeling deprived. The dose escalation tends to deepen the effect. This is the phase where weight loss on the scales begins to feel real and consistent.

In the STEP 1 trial published in the New England Journal of Medicine, participants lost an average of around 15% of body weight over 68 weeks. The bulk of that loss accumulated through the middle months, not the first fortnight. That context matters when your week-six weigh-in looks less impressive than you hoped.

Side effects are often most noticeable in this window too. Nausea, loose stools, or a feeling of fullness that tips into discomfort are common after dose increases. They generally settle within a week or two as your body acclimatises. If they are persistent or severe, that is a conversation for your prescribing team, not something to push through silently. You can find a fuller run-down of what to watch for on our page covering what happens on Wegovy.

One practical note: if you are injecting on a fixed day each week, keeping the timing consistent helps maintain steady semaglutide levels. Many people find anchoring it to a weekly routine (a Sunday, say, before the week gets busy) makes it easier to stick to.

Months three to six and beyond: where the real picture emerges

The 2.4 mg maintenance dose is usually reached at around week seventeen of the standard titration schedule. From that point, the full clinical effect of Wegovy becomes apparent. Weight loss that looked slow in the early weeks compounds over time: a 2% reduction in month two, another 3% in month four, and so on until the body reaches a new equilibrium.

The NHS semaglutide information page notes that if you have not lost at least 5% of your body weight after six months on the maintenance dose, your prescriber will review whether to continue. That clinical checkpoint is built into the treatment, not a failure on your part, it reflects the evidence-based approach to prescribing these medicines responsibly.

It is also worth knowing that results vary considerably between individuals. Genetics, starting weight, metabolic history, dietary habits and how consistently the medicine is taken all play a role. Trials report population averages; your trajectory will be your own. If you are weighing up Wegovy against other licensed options, the semaglutide overview and a look at our weight-loss treatment options set out the landscape clearly.

One thing patients sometimes raise after a few months is hair shedding, a topic our page on hair loss on Wegovy addresses directly, including why it happens and when it tends to resolve.

Treatment cost is a practical consideration for many people. Our Wegovy cost guide explains what a legitimate private prescription includes and how to read market pricing sensibly.

If you have questions about whether Wegovy is clinically right for your situation, starting a free consultation with our prescribers is the straightforward next step. A real clinician reviews your answers the same day, no algorithms, no automated decisions.