Your First Week on Wegovy: What Actually Happens

The moment you give your first injection

You've chosen your day. Most people pick a morning that suits their routine, a Saturday, say, or a Sunday when they're not rushing. You give the first 0.25 mg dose and then... you wait for something dramatic that mostly doesn't arrive. The first day on Wegovy is often unremarkable, which is exactly how it should be.

Semaglutide, the active ingredient, is a GLP-1 receptor agonist. It mimics a gut hormone involved in appetite regulation and slows the rate at which the stomach empties. At 0.25 mg that signal is gentle. You might notice your appetite feels slightly blunted a few hours after the injection, or you might notice almost nothing. Both are normal. Some people feel a mild wave of nausea in the afternoon or evening of injection day; others don't. The NHS medicines page for semaglutide lists nausea, vomiting, diarrhoea, constipation and indigestion as the most common early effects, and all are described as typically mild to moderate. They tend to be worst in the 12–24 hours after the jab and then recede.

Practical tip from people who've been through it: eating smaller amounts, avoiding very rich or fatty food on injection day, and keeping well hydrated all help. A useful detail, some people keep their pen in the fridge door, take it out 30 minutes before injecting to bring it closer to room temperature, and find the injection more comfortable as a result. Store it refrigerated between 2–8°C and follow the storage guidance in your leaflet exactly.

What your body is actually doing during Wegovy week 1

Beneath the surface, semaglutide is binding to GLP-1 receptors in the gut, pancreas and brain. It increases insulin release in response to food, reduces glucagon secretion, and sends satiety signals to the hypothalamus. You may start eating a little less without consciously trying. Portions that felt normal before might feel slightly large. That is the medicine working as intended, but at the starter dose, the effect is subtle.

There is no appetite crash in week one for most people. The titration schedule (moving from 0.25 mg up through 0.5 mg, 1.0 mg, 1.7 mg and eventually 2.4 mg (or the newer 7.2 mg maintenance dose)) exists precisely because the body needs time to adapt at each level. Rushing that ladder produces more side effects; the slower ascent produces better long-term tolerability. That is why the STEP 1 trial, published in the New England Journal of Medicine, ran for 68 weeks before its headline results were measured. Week one is the very first rung. For more detail on what semaglutide does and how its licensed schedule works, the Wegovy overview page covers it fully.

Some people also feel mild fatigue or a low-grade headache in the first few days. These are listed side effects and usually pass. Staying hydrated matters more than most people realise; GI effects reduce fluid intake and that compounds tiredness quickly.

Nausea in week one: when it's expected and when to act

Nausea is the side effect that dominates first-week conversations, and it is worth being honest about it. Most people do experience at least some. Most also find it manageable and self-limiting. The NHS guidance on semaglutide notes that GI side effects are typically most noticeable after starting or after a dose increase and tend to settle within a few days to a couple of weeks.

What the research describes as common, though, is not the same as what you will necessarily experience. Some people sail through week one without a moment of queasiness. Some find it peaks on day two. The pattern varies, and your prescriber should be your first call if symptoms feel disproportionate, persist beyond a week, or if you develop severe and persistent stomach pain that radiates toward your back, that warrants urgent medical attention given what we know about pancreatitis as a rare but serious risk with GLP-1 medicines.

You can also browse frequently asked questions on our site, or get in touch with our team if you are a current patient and want to speak to someone. For those curious about how things tend to shift as weeks pass, the fifth week on Wegovy is often where appetite suppression starts feeling more consistent.

Setting realistic expectations for the weeks ahead

Week one is foundation-laying. It is not where you measure the medicine's success. Clinical trials produce their results over many months; expecting visible change in seven days sets a benchmark the evidence has never supported. What you can reasonably expect by the end of your first week: some adjustment in appetite, possibly some GI discomfort you are learning to manage, and a growing sense of the routine this treatment requires.

Later weeks tend to feel different. By week six and week seven, many people report the medicine feeling more integrated into daily life. Appetite patterns are clearer. Side effects, for those who had them, are usually reducing. And the dose titration, when it happens, is done with prescriber oversight, not automatically. Questions about food choices as treatment progresses, including things like eating normally on Wegovy, come up a lot. The short answer is that no foods are banned, but appetite often reshapes what feels satisfying.

Wegovy is a prescription-only medicine. If you are considering starting treatment and want to understand whether it might be appropriate for you, a prescriber needs to assess your health picture in full. You can explore the available weight-loss treatment options and start a free consultation with our team. Our prescribers review every application the same day, a real clinician reads your answers, not automated software.