Your First Week on Wegovy: A Realistic Picture

Step 1, Injection day itself (day one)

You have your pen in the fridge, you have read the instructions, and day one arrives. The 0.25 mg dose goes in (abdomen, thigh or upper arm, rotated each week) and for many people nothing dramatic happens in the hours that follow. Some notice a slight dulling of appetite by evening; others feel nothing at all. Both responses are normal at this stage.

What the starting dose is actually doing is priming your GLP-1 receptors gradually so that, when the dose increases in later months, your digestive system is less likely to object loudly. The semaglutide first-week experience varies quite a bit from person to person, partly because of differences in gut sensitivity rather than any indicator of whether the medicine will work for you long-term.

If you notice mild nausea on injection day, eating a small portion rather than a full meal tends to help. Staying well hydrated matters too. These are practical adjustments, not medical advice, your prescriber and the Patient Information Leaflet are the right guides for your specific situation. The full picture of what to expect covers each of these in more detail.

Step 2, Days two to four: the GI window

If side effects are going to appear in the first week of Wegovy, days two to four are when most people encounter them. Nausea is the most commonly reported, followed by constipation or loose stools, burping, and a feeling of fullness that lingers longer than usual after eating. In clinical studies of semaglutide, gastrointestinal symptoms were the most frequently reported adverse effects, particularly at the start of treatment and after each dose increase, as documented in the NHS patient information on semaglutide.

Crucially, these symptoms are typically mild to moderate and transient. They tend to ease within a few days as the body adjusts. If vomiting is severe or you cannot keep fluids down, that warrants contact with your prescribing team. Pancreatitis is a rare but serious side effect of GLP-1 medicines; the MHRA flagged it in a January 2026 Drug Safety Update, the signal to act is severe, persistent abdominal pain that spreads to the back, with or without vomiting. That should prompt urgent medical attention, not a wait-and-see approach.

For most people, though, days two to four are simply a period of adjustment. Smaller meals, lower-fat foods and keeping carbohydrates moderate tend to reduce GI burden. Your prescriber can advise further if symptoms are troublesome.

Step 3, Days five to seven: appetite signals start shifting

Towards the end of the first week, some people begin to notice that they feel full sooner than expected, or that the pull towards snacking is slightly quieter. This is encouraging, though it does not always happen this soon. Appetite suppression builds gradually as semaglutide reaches a steady state, which takes several weeks of consistent dosing.

Weight on the scale at day seven is unlikely to reflect fat loss. Any reduction is most likely water, partly from lower carbohydrate intake when appetite dips. That is not a failure, the STEP 1 trial, published in the New England Journal of Medicine, showed an average reduction of around 15% of body weight over 68 weeks at the 2.4 mg maintenance dose; the first week represents just the beginning of that process. Questions about whether weight actually shifts in week one are among the most common our clinical team hears, and the honest answer is: rarely in a measurable way, and that is fine.

If you are wondering how to support the process from the start, our guide on getting the most from Wegovy alongside lifestyle changes covers nutrition and activity in practical terms. And if you are still researching whether the treatment is right for you, the Wegovy overview sets out the full picture, including eligibility and how the treatment is accessed through a regulated pharmacy. For context on what the treatment costs privately, the Wegovy cost page explains what a legitimate price includes and how to read it.

What week one tells you, and what it does not

A quiet first week is not a sign the medicine is not working. A difficult first week is not a sign it will stay difficult. Both interpretations are common and both are usually wrong. The first seven days are almost entirely about tolerability (establishing that the starting dose suits you) not about results.

The results that most people see tend to accumulate between weeks four and twelve, with the clearest trajectory visible by month three. Patience in the first week is, genuinely, part of the clinical logic. Our prescribers review your progress before any repeat supply, that oversight is how dose increases happen safely and at the right pace. If you have questions about how week one compares to what others experience, the data on early weight loss patterns gives a grounded view without over-promising.

Wegovy is a prescription-only medicine assessed and dispensed through a GPhC-registered pharmacy; every prescription is reviewed by a real clinician. If you are considering starting, speak to our prescribers through a free consultation, assessed the same day you apply.