Semaglutide Week 3: What Most People Notice at This Stage

Step 1: Understanding where week 3 sits in the starter phase

Wegovy's dosing schedule begins at 0.25 mg weekly for four weeks. That first month is deliberately cautious, the starter dose is there to settle your system into the medicine, reducing the chance of nausea or other GI discomfort before your prescriber considers moving higher. Week 3 is the penultimate injection of that opening phase.

Because semaglutide accumulates in the body over repeated weekly doses, the concentration in your system is meaningfully higher by day 21 than it was after your first injection. That accumulation is part of why appetite changes often feel more pronounced around this point than they did in week 1, and if you want to revisit what was happening at that earlier stage, our guide on what to expect during semaglutide week 1 explains how that first injection typically unfolds. Some people describe a clear shift in how much they want to eat; others notice they feel full after smaller portions. Some barely register a change yet. All of those responses are within the normal range at this stage.

If you want a frame of reference for how early weeks compare, the detail on what week 2 of semaglutide involves outlines the patterns from the previous injection, and it is worth reading alongside this page.

Step 2: What to track during week 3 of semaglutide

This is a practical week for observation. Your prescriber will want to understand how you are tolerating the 0.25 mg dose before confirming your next step, so keeping a simple note of a few things can be genuinely useful.

Appetite and eating patterns are the most obvious thing to watch. Are you eating less without effort, or forcing yourself? Are you stopping mid-meal? These are meaningful signals. Hydration matters too, GI symptoms can reduce your desire to drink, and staying adequately hydrated supports how the medicine works. The Wegovy treatment overview covers the broader lifestyle context that sits alongside the injection.

On the side-effect front, nausea, loose stools or constipation that started earlier in the course often begin to settle during the third week. They do not disappear for everyone, and if they remain difficult, your prescriber would rather know now than after another few weeks. Injection-site reactions (mild redness or tenderness) are also worth noting but are common and usually brief. The NHS's patient-level information on semaglutide covers the full side-effect profile and is worth reading: NHS guidance on semaglutide.

One thing people often tell us they wish they had known: week 3 is rarely the week for dramatic numbers on the scale, and if you are curious about what changes people typically notice in their first seven days, our page covering semaglutide 1 week results puts those early figures into perspective. Early weight change on semaglutide is partly fluid shifts and partly the beginning of a reduced-calorie intake. Seeing very little on the scale does not mean the medicine is not working.

Step 3: What the clinical evidence says about early results

The STEP 1 trial (the pivotal phase 3 study for semaglutide 2.4 mg, published in the New England Journal of Medicine) tracked participants over 68 weeks. Average weight reduction across the trial reached around 15%. Week 3 figures were not reported in isolation, but the trial's trajectory makes clear that meaningful weight loss accumulates gradually over months, not in the first few injections.

That context matters if you are comparing your week 3 experience against what you hoped for. The dose you are on now is the lowest in the schedule. Most of the medicine's effect builds as the dose titrates upward, and that process has barely begun. For a sense of the longer arc, how long Wegovy takes to work gives a realistic picture of the timeline most people follow.

For those further into their Wegovy journey who want to understand the trajectory beyond the first month, our page on what week 4 of semaglutide looks like covers what typically changes as the starter phase closes.

When to get medical help

Most people move through week 3 without any cause for concern. There are, however, symptoms that warrant prompt medical attention regardless of where you are in your treatment. Severe, persistent stomach pain (particularly if it spreads to your back) needs same-day medical assessment, as it can indicate pancreatitis, a known but uncommon side effect of GLP-1 medicines. Signs of a serious allergic reaction (swelling of the face, throat or tongue; difficulty breathing) require emergency care.

Persistent vomiting or diarrhoea that is stopping you from drinking enough is also worth acting on quickly, since dehydration can affect your kidneys. The MHRA's Yellow Card scheme lets you report any suspected side effects: Yellow Card reporting. If you are ever unsure, contact your prescriber or call NHS 111.

If you are considering starting semaglutide and want to understand how treatment is assessed, checking your eligibility with our prescribers is the straightforward next step. It is a free consultation, reviewed by a real clinician the same day.