How to use Wegovy for weight loss: what actually happens week by week

The pen is sitting in your fridge. Here's what happens next.

Picture the scene: your first Wegovy pen has arrived, it's been in the fridge overnight, and you're reading the leaflet at the kitchen table wondering whether you're doing this right. The starting dose is 0.25 mg, and it's worth knowing that this isn't the dose that produces weight loss, it exists purely to let your digestive system adjust gradually. Most people feel relatively little at 0.25 mg, which is exactly the point.

Each pen delivers four doses, one per week on your chosen day, and if you're unsure about the schedule, this guide on how often you take Wegovy walks through the weekly rhythm in detail. You take the pen out of the fridge around 30 minutes before use so it reaches room temperature, then inject into the fatty tissue of your abdomen, thigh or upper arm. The needle is short and fine; many people are nervous the first time and surprised by how straightforward it turns out to be. You'll find thorough step-by-step detail on the physical process in the guide to taking Wegovy injections, including how to rotate sites safely.

After four weeks, your prescriber reviews your progress and, if you're tolerating the medicine well, moves you up to 0.5 mg. The titration continues (1.0 mg, then 1.7 mg, then 2.4 mg) each step roughly four weeks apart. The MHRA has also approved a 7.2 mg maintenance dose for eligible adults, available via a dedicated single-dose pen. Which maintenance dose is right for you is a clinical decision, not a choice you make independently. The NHS semaglutide page has a clear overview of how semaglutide works and what the dose schedule involves.

What Wegovy is actually doing while you lose weight

There's a common misconception that these injections simply suppress appetite through willpower-by-proxy, that you're just not hungry because the drug is tricking you. The reality is more interesting. Semaglutide mimics a gut hormone called GLP-1, which your body naturally releases after eating. It signals to the brain that you're full, slows the rate at which food leaves your stomach, and reduces the intensity of food-related thoughts that drive overeating for many people. The full mechanism behind Wegovy's effects is worth understanding if you want to make sense of what you're experiencing.

This mechanism is why using Wegovy for weight loss isn't just about the injection. The medicine lowers the biological drive to overeat; you still need to give it something to work with. A diet that keeps protein intake reasonable (to protect muscle mass during weight loss) and doesn't rely on very-high-fat meals (which can worsen nausea early on) tends to produce the best results. The same is true of keeping up some form of physical activity, even light walking. These aren't optional extras bolted on for show; they're part of how the treatment is licensed to be used.

In the STEP 1 trial, adults taking semaglutide 2.4 mg alongside lifestyle changes achieved an average weight reduction of around 15% over 68 weeks, as published in the New England Journal of Medicine. Results vary between individuals, and no one can guarantee what your outcome will be, but the evidence base is solid.

Side effects: what to expect and when to act

Most side effects from Wegovy are gastrointestinal. Nausea is the most frequently reported, followed by constipation, diarrhoea, indigestion and burping. They tend to peak in the first week or two after a dose increase and ease considerably once your body acclimatises, one reason the titration schedule exists rather than starting at a therapeutic dose straight away.

Practical things that help: eating smaller portions, avoiding very fatty or very spicy food in the early weeks, staying well hydrated, and not lying down immediately after eating. Fatigue and mild headaches are also reported, particularly in the first month. Injection-site redness or mild discomfort is normal and usually transient.

There are symptoms that warrant prompt medical attention. Severe, persistent stomach pain that spreads to the back (with or without vomiting) should be assessed urgently; in January 2026 the MHRA issued a Drug Safety Update specifically highlighting acute pancreatitis as a known, though infrequent, risk with GLP-1 medicines. Symptoms of an allergic reaction (swelling, difficulty breathing, rapid heartbeat) also require immediate help. You can report any suspected side effects through the MHRA Yellow Card scheme.

It's also worth noting that Wegovy is not recommended during pregnancy, while breastfeeding, or when actively trying to conceive. Women taking oral contraceptives alongside tirzepatide face a specific absorption consideration, though the same interaction evidence is less pronounced for semaglutide, discuss your full contraceptive picture with your prescriber either way. Anyone under 18 is outside the licensed age range.

Getting started: what the prescription process looks like

Wegovy is a prescription-only medicine, so the first step is always a clinical consultation, and our guide on how to get Wegovy explains exactly what that process involves. On the weight-loss treatment overview, you can see which medicines are currently available and roughly who they suit. If you're wondering about what Wegovy costs privately in the UK, prices vary by dose and provider, any legitimate price includes the clinical assessment and prescription, not just the pen.

At nume, every consultation is read the same day by a GPhC-registered Independent Prescriber, a real clinician, not automated software. If you're approved, your treatment is dispatched the same day (for orders placed before noon, Monday to Friday) and delivered free the next working day in plain, unbranded packaging. There are no hidden fees and no subscription; every repeat order is clinically re-reviewed before it ships.

If you want to understand more about semaglutide's role in weight management before committing to anything, that's the sensible starting point. Ready to find out whether Wegovy is clinically suitable for you? Start your free consultation with our prescribers today.