What to Expect in Your First Month on Wegovy

Week 1: the first injection and what your body is doing

Most people inject on a set day each week, Sunday evening, say, or a Monday morning before the working week starts. Picking a consistent day that isn't likely to shift (payday Fridays are often disrupted) helps the routine stick. Within a day or two of that first 0.25 mg injection, some people notice a flicker of nausea, particularly after eating a larger meal than usual. Others feel nothing at all. Both responses are normal.

What is happening physiologically is meaningful even if the scales aren't moving. Semaglutide binds to GLP-1 receptors in the gut and brain, slowing gastric emptying and signalling to the brain's appetite centres that energy stores are adequate. That signalling effect can reduce hunger noticeably from week one, the appetite shift sometimes arrives before any weight change does. If you want a thorough look at what your first week on Wegovy is likely to involve, that detail is covered separately, including how the first injection tends to feel and what most people notice in the days that follow. If you want a thorough look at what the first day of Wegovy feels like, that detail is covered separately.

Keep meals moderate in fat and portion size in week one. Not because the medicine requires a special diet, but because large or rich meals amplify nausea at this stage. Protein and vegetables tend to sit better than heavy carbohydrates. Hydration matters throughout treatment; the NHS advises contact with a healthcare professional for any signs of severe dehydration from persistent vomiting or diarrhoea.

Weeks 2–3: side effects peak (and usually begin to settle)

For most people, weeks two and three represent the trickiest stretch. You are still on 0.25 mg, the body hasn't fully adapted, and GI symptoms (nausea, belching, looser stools, constipation, or a general sense of digestive slowness) may be more pronounced than in week one. This is the phase people most commonly describe as "the adjustment period", and it is exactly what the starter dose is designed to cushion.

Clinically important symptoms to watch for beyond ordinary GI discomfort: severe or persistent abdominal pain that spreads to the back, which can indicate pancreatitis and requires urgent medical attention. The MHRA issued a Drug Safety Update in January 2026 flagging acute pancreatitis as an infrequent but serious known side effect of GLP-1 medicines. If that symptom pattern arises, seek help promptly rather than waiting for your next check-in. You can also report any suspected side effects via the MHRA Yellow Card scheme.

Appetite suppression usually deepens through weeks two and three. Meals feel satisfying on smaller portions. Some people find they skip snacks naturally rather than through effort. Reading about what to expect after your first Wegovy shot can help you recognise which changes are typical and which are worth flagging to your prescriber, but the effect often intensifies as the second week progresses. Weight loss in weeks two and three can be modest (fluid shifts and reduced intake combine) but the scale is rarely the most useful thing to track at this point.

Week 4: the first dose review and what the numbers might show

At the end of week four, you have completed your starter dose. Your prescriber will review whether to move to 0.5 mg. That review isn't automatic, it depends on how well you've tolerated the current dose and your overall clinical picture. At nume, a named prescriber reviews each repeat before it is approved, rather than approving repeats by default.

Weight loss by the end of week four is variable and often modest, somewhere between 1 kg and 4 kg for many people, sometimes less, occasionally more. The STEP 1 trial, published in the New England Journal of Medicine, showed an average of around 15% body weight reduction over 68 weeks at the 2.4 mg maintenance dose, a figure that reflects the entire treatment course, not the first month. Understanding how long Wegovy takes to work properly is important context here: the medicine builds effect gradually over months of dose escalation, not weeks at the starting level.

By week four, many people have also settled into the injection routine. Rotation of sites (abdomen, thigh, upper arm) reduces localised reactions. The pen is kept refrigerated between doses; the patient information leaflet gives the exact room-temperature window for short-term storage if you need to travel. Our frequently asked questions page covers common practicalities around storage and travel.

What the first month doesn't tell you, and what to do next

The first month is the least representative part of Wegovy treatment. You are on the lowest dose, your body is adjusting, and results are typically the slowest they will ever be. Drawing conclusions about whether Wegovy is working for you based on four weeks at 0.25 mg would be like judging a book by the copyright page.

Appetite change, improved relationship with food, and early modest weight movement are the meaningful signals to look for at this stage, and what you should expect in the first week of Wegovy sets helpful benchmarks for telling the two apart. Detailed guidance on the full trajectory is on our Wegovy: what to expect overview, and if you're weighing up treatment options more broadly, the weight-loss treatment overview covers what's currently licensed in the UK.

For anyone still deciding whether to begin, or looking to transfer from another provider, the starting point is always a clinical assessment. Semaglutide (Wegovy) is a prescription-only medicine; a prescriber must review your medical history, current medications and BMI before it can be supplied. If you'd like to find out whether you're eligible, you can check your eligibility with our clinical team through a free consultation, reviewed the same day by a GPhC-registered prescriber.