Wegovy week 1 weight loss: what's actually happening in your body

You've done the first injection, and the scales look exactly the same

Picture this: you've carefully stored your pen in the fridge, picked your injection site, done everything right, and on day seven you step on the scales expecting something. Nothing. Maybe half a pound. Possibly a small gain from water retention or a heavier meal the night before.

This is the normal week 1 experience for most people on Wegovy, and our page on what to expect from first week Wegovy weight loss explains why the starting numbers rarely tell the full story. The starting dose (0.25mg) exists purely to let your gut, your hormones and your appetite signals adapt to a new GLP-1 receptor agonist. At that dose, semaglutide is barely touching your appetite centres in any consistent way. Some people feel a mild reduction in hunger by day three or four; plenty feel nothing different at all until they're several weeks in.

What is happening, even when the scale is quiet, is physiological. Semaglutide is beginning to influence gastric emptying, food moves through your stomach more slowly, which is part of why nausea can appear early. Your pancreas and gut are adjusting to a signal they haven't received before. That adjustment period is necessary. Skipping it by starting higher would simply mean more severe side effects with no therapeutic benefit to show for it.

The practical habit worth building in week 1: weigh yourself once, at the same time of day, on the same scale, with the same amount of clothing. Midweek morning, after the loo, before breakfast. Then step away from the scale for the rest of the week. Daily weighing in week 1 generates noise, not data, natural fluctuations of 1–2 kg are routine and have nothing to do with the medicine.

Why week 1 side effects often feel louder than the results

Nausea is the side effect most people mention first, and it tends to peak in the 12–48 hours after that initial injection. Loose stools, bloating, burping and a vague sense of fullness after small amounts of food are all part of the same picture, semaglutide slowing gastric emptying faster than your gut expected.

These effects are almost always mild to moderate and settle within a few days for most people. Eating smaller portions, choosing blander foods, and staying well hydrated all help. If nausea is making it difficult to keep fluids down, or you develop severe stomach pain that reaches into your back, those are reasons to contact your prescriber promptly rather than waiting it out. The MHRA's Yellow Card scheme exists for reporting any unexpected reactions too.

Here's the thing most people find reassuring in hindsight: the side effects being noticeable in week 1 doesn't mean week 2 will be worse. For a large proportion of people, week 1 is the peak of GI disruption, precisely because the dose stays at 0.25mg for the full first four weeks. Your body gets time to catch up. If you're concerned about how side effects are tracking, our frequently asked questions cover the most common week 1 experiences, and our prescribers are available seven days a week.

What week 1 is actually setting up, and when the results arrive

The STEP 1 trial, published in the New England Journal of Medicine, followed 1,961 adults with obesity or overweight over 68 weeks on semaglutide 2.4mg alongside lifestyle changes. Average weight reduction reached around 15% of body weight. That number comes from a process that started somewhere very like your week 1: slow titration, modest early change, then a sustained downward trend as the maintenance dose kicks in.

Most people begin noticing consistent appetite suppression somewhere between weeks four and eight, often coinciding with the first dose increase to 0.5mg. The weight loss that follows tends to feel more deliberate by that point: smaller portions feel genuinely satisfying, the urge to snack fades, and the scale starts to move in a direction that matches the effort. A closer look at how weight loss on Wegovy progresses over time shows that the trajectory is rarely linear, but the trend becomes clearer after the first month.

If you're already thinking about what week 2 might look like, our page on no weight loss in week 2 covers what's normal at that stage. If the scale still hasn't shifted by your third injection, our guide to no weight loss at week 3 on Wegovy explains what that means and when to take it seriously. And for anyone curious about the longer arc, week 5 results on Wegovy gives a sense of how the picture shifts after the first dose increase. The full timeline (from first injection to meaningful change) is covered in detail at how long Wegovy takes to work.

Wegovy is a prescription-only medicine. Every person who starts it through nume has had their consultation personally reviewed by a GPhC-registered Independent Prescriber, a clinician reads your answers, not a piece of software. If you're still deciding whether Wegovy is the right path, the treatment overview is a good starting point, or you can explore weight loss treatment options more broadly. Our clinical team's approach is outlined at our clinical lead's profile. When you're ready to take the next step, speak to our prescribers by starting your free consultation.