What Happens in Week 3 on Wegovy

What the trial data tells us about the early weeks

The STEP 1 trial, which followed 1,961 adults over 68 weeks, didn't publish week-by-week breakdowns in granular detail, but the trajectory is clear: weight loss and appetite reduction both accumulate over months, not the first few injections. Semaglutide, the active ingredient in Wegovy, is a GLP-1 receptor agonist. It slows how quickly the stomach empties and acts on appetite-regulating signals in the brain. At 0.25 mg, the starting dose, semaglutide concentrations in the body are building toward a working level, which is why most prescribers describe the first four weeks as an adjustment phase rather than an active treatment phase. The average weight reduction across the full STEP 1 trial reached approximately 15% of body weight by week 68 at the 2.4 mg maintenance dose. Week 3 sits at the very beginning of that arc. That context matters, not to manage expectations downward, but to stop people drawing the wrong conclusions from a number on the scales at day 21. The NHS medicines page for semaglutide explains this titration approach and why it exists.

Side effects at week 3: what's normal and what needs attention

A question our prescribers hear most weeks is some version of: "I still feel sick, is that normal at week 3?" The honest answer is that gastrointestinal side effects, particularly nausea, loose stools, constipation and indigestion, are most pronounced during the early starter period and tend to settle as the weeks pass. Most people find them manageable by eating smaller portions, avoiding rich or greasy food, and staying well hydrated. They don't disappear for everyone at exactly the same point. If symptoms are making it hard to eat or drink adequately, that's worth flagging to your clinical team sooner rather than later, dehydration can compound other problems. The side effects that should prompt urgent medical attention are different in character: severe, persistent stomach pain that spreads toward the back could indicate pancreatitis, which the MHRA highlighted in a Drug Safety Update for GLP-1 medicines in January 2026. Signs of a serious allergic reaction, such as swelling of the face or throat or difficulty breathing, also need emergency care. For a fuller picture of what to watch for, the NHS semaglutide guidance sets these out clearly. You can also report any suspected side effects at the MHRA's Yellow Card service.

Weight change at week 3: reading the scales honestly

Some people lose a noticeable amount in the first three weeks; others see very little movement. Both are consistent with how semaglutide works. Early reductions often reflect water loss or a shift in eating patterns rather than fat loss driven by the medicine at full effect. The rate of weight loss on Wegovy varies considerably between individuals, shaped by starting weight, diet, activity and how their body responds to the medicine. Weighing yourself at the same time of day, once a week, gives more useful information than daily readings. If you're curious about what week 3 results might look like compared to later milestones, the broader week-by-week results picture puts individual data points in perspective. It's also worth reading about how long Wegovy typically takes to show a meaningful effect, the honest timeline is longer than many people expect going in.

Practical things worth doing in week 3

Week 3 is a good moment to reflect on the habits that work alongside the medicine, not instead of it. Protein at each meal helps preserve muscle while weight falls; fibre supports gut comfort; and keeping alcohol low reduces nausea. If the injection itself is causing concern (technique, site rotation, or what to do with used needles) the Patient Information Leaflet inside your pen covers each step, and our aftercare team is available seven days a week. Looking back, week 1 and week 2 often feel very different in retrospect once you know what was happening physiologically. Looking ahead, week 4 marks the end of the starter period for most people, the point at which dose progression becomes a clinical conversation. For context on what that progression looks like and what the Wegovy treatment journey involves, the Wegovy overview covers the full picture. If you're weighing up the cost of staying the course privately, the cost context for Wegovy in the UK addresses what private treatment actually includes. The most important thing at week 3 is simple: keep going, stay in contact with your clinical team, and don't benchmark yourself against someone else's day 21.