What Happens in Your First Week on Semaglutide

Is what I am feeling normal, or a reason to stop?

This is the question almost everyone asks in the first few days. The short answer: mild to moderate nausea, a reduced appetite, some fatigue, and loose stools are all commonly reported and are consistent with what the NHS patient information for semaglutide describes as expected early reactions. They are the result of slowed gastric emptying, food moves through your stomach more slowly, which suppresses appetite but can also leave you feeling unsettled.

Symptoms that require you to contact a doctor straight away are different in character: severe, persistent stomach pain that radiates toward the back (a potential sign of pancreatitis), signs of a serious allergic reaction, or significant vomiting that leaves you unable to keep fluids down. For side effects you are unsure about, the semaglutide overview on the nume site covers the full profile in detail, and the Yellow Card scheme at yellowcard.mhra.gov.uk lets you report anything unexpected directly to the MHRA.

One practical check worth doing: after your first injection, note the time and jot down what you ate in the hours before. Injecting after a large, fatty meal consistently worsens nausea for many people. A light meal or plain snack beforehand makes a measurable difference for most. That is a habit you can establish in under a minute, and it pays off at every dose increase too.

Should I push through the side effects or adjust what I am doing?

Week one is rarely the week to question whether the medicine is working. The starting dose of 0.25 mg exists precisely because the higher doses needed for meaningful weight reduction come with a steeper GI adjustment; the first four weeks are the buffer. What you can reasonably adjust is behaviour around the dose: smaller, lower-fat meals; staying upright for a couple of hours after eating; keeping hydrated with water even when appetite for food is low.

What you should not adjust unilaterally is the dose itself, the injection timing within your weekly schedule, or whether to continue at all if you are managing symptoms. Those decisions belong with your prescriber. If you started through Wegovy and have questions in these first days, your clinical team should be reachable, at nume, prescriber-led aftercare runs seven days a week precisely because questions do not wait for Monday morning.

The week-by-week picture changes considerably once titration begins. The Wegovy week-by-week guide maps out how most people's experience shifts from month to month, which can make the early discomfort easier to contextualise.

How much weight should I expect to lose in week one?

Probably none, and that is not a failure. The STEP 1 trial (68 weeks, semaglutide 2.4 mg versus placebo) recorded an average body-weight reduction of around 15% over the full course of treatment, published in the New England Journal of Medicine. That reduction accumulated steadily over months, not days. Week one at 0.25 mg contributes essentially nothing to that trajectory on its own.

What week one does contribute is your body's baseline tolerance to the medicine. People who have a rough first week occasionally reduce their food intake simply because eating feels uncomfortable, a small incidental effect, not a reliable one. Meaningful appetite suppression builds as the dose increases toward the 1.7 mg and 2.4 mg maintenance levels. For context on the longer arc, the first week on Wegovy page explores what the experience looks like across the full starting phase.

If cost is part of your planning, the Wegovy pricing page sets out what private treatment typically involves across the dose schedule. Understanding that upfront helps you plan realistically for the months when the medicine is actually doing its work.

What does week one tell you about the weeks ahead?

Quite a lot, actually. The pattern of side effects in week one (their timing relative to the injection, their severity, and how quickly they resolve) tends to repeat in a milder form at each subsequent dose increase. If nausea hit hardest about six hours after your first injection and cleared by day three, that is a useful calibration point. You will likely see a version of it again at 0.5 mg, briefer each time for most people.

The first day is its own chapter. The first day on Wegovy page goes into the specific hours after that initial dose for anyone who wants a finer-grained picture. And if you are wondering what week five feels like once the dose has moved on, week five on Wegovy gives a realistic account of where most people land once tolerance is established.

Week one is, in the end, a settling-in period. The medicine is prescription-only for good reason: what happens in these early weeks is worth having a clinician's eye on, not just a forum thread. If you would like to begin, or if you are weighing up whether Wegovy is the right fit for your circumstances, our prescribers are ready to review your case. Speak to our prescribers through a free consultation, reviewed the same day by a GPhC-registered Independent Prescriber, not a bot.