How fast does Wegovy work — and what does the evidence actually show?

What STEP 1 shows about when weight loss actually begins

The clearest picture of how fast Wegovy starts working comes from the STEP 1 trial: 1,961 adults with obesity or overweight and at least one weight-related condition, 68 weeks of treatment, semaglutide 2.4mg against placebo. Weight loss did not happen in a single dramatic drop. At four weeks, participants had lost roughly 1–2% of body weight on average. By week 16 the curve was steepening. The majority of the trial's total 15% average loss accumulated between months three and twelve, after the maintenance dose had been reached and stabilised.

This matters because a lot of people weigh themselves at the end of week two and feel nothing is happening. Something usually is, appetite signals change before fat mass does. What to expect in the second week of Wegovy is a question worth understanding in its own right, because the early phase feels quite different from the middle phase of treatment.

The NHS semaglutide medicines page notes that it can take several weeks before you notice a change in your weight, and that the medicine works best alongside a reduced-calorie diet and increased physical activity. That framing is accurate and useful: the medicine reduces appetite, but the weight loss itself follows from eating less and moving more.

How the dose schedule shapes the timeline

Wegovy does not start at its full therapeutic strength. The prescriber-directed titration runs from 0.25mg up through 0.5mg, 1.0mg and 1.7mg before reaching the 2.4mg maintenance dose, with roughly four weeks at each step. That means you are not at maintenance until around week sixteen at the earliest. The graduated schedule is not bureaucratic caution, it gives your digestive system time to settle, and the side-effect profile at 2.4mg is considerably better tolerated by people who have worked up to it slowly.

The practical consequence for timeline expectations is straightforward: if someone tells you Wegovy did not work after six weeks, they were still in the dose-adjustment phase. Judging the medicine's effectiveness before you have been at maintenance for at least a few months is genuinely premature.

A higher-dose option is now available: the MHRA approved a 7.2mg semaglutide pen in April 2026 for adults with a BMI of 30 or above, with trial data reporting an average weight loss of around 20.7% over 72 weeks. The titration pathway to that dose is longer still. How long Wegovy takes to work at each dose level is a question worth exploring if you are at an earlier stage of treatment.

Reading your own progress: a one-minute check that helps

Weekly weigh-ins can be misleading because weight fluctuates daily by up to 2kg depending on hydration, hormones and what you ate. A more useful habit takes under a minute: log your weight on the same morning each week, in the same conditions (first thing, before eating, after using the bathroom) and look at the four-week rolling average rather than the week-on-week number. That average smooths out the noise and shows the actual direction of travel far more clearly than any single reading.

If you are thinking about what Wegovy costs as a private prescription, the Wegovy pricing page sets out what the market looks like and what a complete service should include. The medicine itself is only part of the picture.

Results across the STEP programme were not uniform. Participants with type 2 diabetes in STEP 2 lost less weight on average than those without, reflecting how underlying metabolic conditions interact with semaglutide's mechanism. How fast semaglutide works for weight loss more broadly (across the full dose range and different populations) is covered separately if you want that wider context.

When to speak to your prescriber rather than wait it out

NICE guidance (TA875) recommends reviewing whether to continue if a patient has lost less than 5% of their starting weight after six months at their maintenance dose. That is a clinical threshold, not a reason to stop early, it exists to make sure the medicine is doing what it should for each individual person.

There are also signs that warrant prompt contact rather than waiting for a scheduled check. Severe, persistent stomach pain that spreads toward the back, with or without vomiting, can indicate pancreatitis, seek urgent medical attention. You can report any suspected side effect through the MHRA's Yellow Card scheme, which helps build the post-market safety record for medicines like Wegovy that are still under additional monitoring.

For people who prefer not to inject, the MHRA approved an oral semaglutide tablet for weight management in June 2026, the first of its kind licensed in the UK. The titration timeline and the way speed of action compares with the injection are explored on the Wegovy treatment page. If you are ready to find out whether you are a suitable candidate for treatment, our prescribers at the consultation page can review your case the same day.