What Happens in Week 4 on Wegovy?

Why does week 4 feel different from the first three weeks?

The first pen of Wegovy contains four weekly 0.25 mg doses. That starting level exists primarily to let your digestive system adapt, not to produce weight loss. By week 4, many people report that the worst of the nausea has passed or at least grown predictable. That predictability matters: you learn your injection-day rhythm, the mild stomach heaviness after meals, the slightly earlier sense of fullness. Some people slot their weekly injection into a weekend morning routine before anything else (a few minutes before the kettle goes on) and by week 4 that habit has usually bedded in.

The NHS medicines page for semaglutide lists nausea, vomiting, diarrhoea, constipation and indigestion as the most commonly reported side effects, and notes that they tend to be worst shortly after starting or increasing a dose. Week 4 sits at the tail end of that initial adjustment window. Not everyone experiences significant symptoms at all; others find them linger a little longer. Neither pattern is unusual.

What often surprises people at this stage is a quieter kind of shift: meals feel satisfying with less food, and the mental noise around eating (the frequency of hunger thoughts) can begin to reduce. It is subtle at week 4. It becomes clearer later.

Should you expect to see weight change by week 4?

Modest weight loss in the first four weeks is possible, and some people do see the scale begin to move. But week 4 is genuinely early. Wegovy's licensed maintenance dose is 2.4 mg weekly; at 0.25 mg, the pharmacological effect on appetite is real but limited. The STEP 1 trial, published in the New England Journal of Medicine, measured outcomes at 68 weeks and found an average reduction of around 15% of body weight at the 2.4 mg dose, a result that builds gradually over many months, not in the first pen.

If you want a realistic picture of what the first month of treatment typically produces, this overview of four-week Wegovy results covers the evidence and practical expectations in more detail. The short version: early changes on the scale are a bonus, not the benchmark. Your prescriber is watching for tolerability and any clinical concerns at this stage, not expecting a transformed number.

People who find week 4 discouraging because the change feels small are often comparing themselves to later-stage results. That comparison is understandable but premature. Understanding how long Wegovy takes to work in full can shift that perspective usefully.

What does a dose increase at week 4 actually involve?

Wegovy's titration pathway moves from 0.25 mg to 0.5 mg after four weeks, then continues upward approximately every four weeks until reaching the 2.4 mg maintenance dose, all under clinical oversight. The prescriber (not you) confirms each step. At a regulated service, that means your week 4 progress is reviewed before the next pen is issued. If side effects have been severe, the prescriber may recommend staying at 0.25 mg for another four weeks. That is a legitimate clinical decision, not a setback.

The practical difference you might notice at 0.5 mg: a temporary return of nausea or other gastrointestinal symptoms as the body adjusts again. This is the same process as week 1, condensed. Most people find each adjustment period shorter than the last. For a sense of what earlier stages involved, week 1 on Wegovy and week 2 describe those patterns specifically. The trajectory matters more than any single week.

On cost: private treatment pricing for Wegovy is shown transparently on the Wegovy cost page, which covers what a legitimate prescription service includes. Prescription medicines should never be sourced without a valid prescription and clinical assessment.

When should week 4 symptoms prompt you to contact a clinician?

Most side effects at week 4 are gastrointestinal and mild. Persistent severe vomiting, significant dehydration, or severe stomach pain that radiates toward the back are different. The MHRA's January 2026 Drug Safety Update on GLP-1 medicines highlighted acute pancreatitis as an infrequent but serious side effect: if you experience that kind of intense, unrelenting abdominal pain, seek urgent medical attention rather than waiting for your next check-in.

Any side effect you are unsure about is worth raising. At a clinician-led service, aftercare support exists precisely for week 4 moments, the unexpected symptom, the question about whether what you are feeling is normal. You can also report suspected side effects directly through the MHRA Yellow Card scheme. A question our prescribers hear regularly at this stage: "is this nausea normal or too much?" The honest answer is that the line is clinical, not something a forum or article can draw for you.

If you are considering starting Wegovy and want a prescriber to assess whether it is right for you, start your free consultation with our team.