Three weeks on Wegovy — what's actually happening in your body

You've just started, here's why it feels underwhelming

Picture this: you've done the consultation, the pen arrived, you've had three injections. You step on the scales and the number hasn't moved much. You might be wondering whether you're one of the people it won't work for. That thought is understandable, and it's also one of the most common misconceptions our prescribers hear, that a quiet first three weeks signals failure.

It doesn't. Wegovy works through semaglutide, a GLP-1 receptor agonist that mimics a gut hormone released after eating. It slows gastric emptying, reduces hunger signals in the brain, and gradually reshapes how appealing food feels. The key word is gradually. The 0.25 mg starting dose is deliberately low, its job is to let your system adapt, not to produce immediate weight loss. The science behind semaglutide is well-established, but the medicine earns its results over months, not weeks.

What you may notice by week three is subtler: a smaller portion feeling filling, less interest in finishing everything on the plate, or meals that used to leave you hungry now leaving you satisfied. These are early signals the medicine is doing something. They're worth paying attention to, even when the scales aren't yet cooperating.

Side effects at three weeks, what's typical and what to watch for

The most commonly reported experiences in the first few weeks are gastrointestinal. Nausea is top of the list, often arriving an hour or two after the injection and settling within a day. Constipation, loose stools, indigestion, burping, any of these can appear and then fade as your dose stabilises. Fatigue and mild headaches are also reported, though less often.

The NHS semaglutide information page notes that these effects are usually mild to moderate and tend to improve as treatment continues. Eating smaller, lower-fat meals and staying well hydrated can make a real difference in week three.

There are symptoms worth acting on quickly. Severe stomach pain that doesn't ease (particularly if it spreads towards your back) should be taken seriously and needs medical attention promptly, given the known association between GLP-1 medicines and acute pancreatitis. Signs of a serious allergic reaction (swelling of the face or throat, difficulty breathing) also require immediate help. The MHRA's Yellow Card reporting scheme exists for anyone who wants to report a suspected side effect to the regulator directly.

If you're finding side effects difficult to manage at week three, the right conversation is with your prescriber, not an adjustment made on your own.

What the weeks ahead look like from here

After four weeks on 0.25 mg, the schedule typically moves to 0.5 mg, then steps upward roughly every four weeks from there, with the prescriber guiding each increase. The significant appetite-reduction effects and measurable weight changes that the clinical trials demonstrated (around 15% average body-weight reduction over 68 weeks in the STEP 1 trial) are built during the maintenance phase, not these early starter weeks.

If you're curious whether things are on track, no weight loss at three weeks is a question we address separately, including what the evidence says about early non-response. Readers further along the journey may find the six-week mark or the eight-week stage more relevant to where they're headed.

It's also worth knowing what Wegovy is not: Ozempic is the same molecule, semaglutide, but is licensed in the UK for type 2 diabetes, not weight management. They are distinct products used in different clinical contexts. The full Wegovy overview covers the licensing clearly if you want to read more.

On the question of cost, private treatment is a significant financial commitment, and the Wegovy cost page sets out what you're actually paying for and why headline prices can be misleading. Understanding that before you start is sensible.

Starting Wegovy through a regulated UK service

Wegovy is a prescription-only medicine. In the UK, the legal route to it is a clinical assessment by a prescriber, who reviews your health history, confirms eligibility, and decides whether treatment is appropriate for you. Private services remove the NHS waiting list, but the clinical rigour doesn't change.

At nume, every consultation is reviewed personally the same day by a GPhC-registered Independent Prescriber. There are no algorithms making prescribing decisions. Identity is verified, weight is confirmed, and treatment dispatched (in plain packaging, via tracked DPD delivery) once clinical approval is given. Our clinical team reviews every repeat order too; there are no automatic renewals.

If you're three weeks in and wondering whether you're on the right path, or if you haven't yet started and want to understand whether Wegovy could be suitable for you, the first step is a conversation with a prescriber, not a set of scales. Check your eligibility with a free consultation at any time.