What to Know Before and When Starting Wegovy

The day your first pen arrives, what to check straight away

Open the box before you do anything else and confirm the pen is intact, the liquid is clear and colourless, and the expiry date hasn't passed. That takes about thirty seconds and matters more than people expect: a damaged pen or one that has been stored outside refrigeration too long should not be used. Wegovy pens must be kept in the fridge at 2–8°C until you need them; the exact room-temperature window once removed is set out in the Patient Information Leaflet inside the box, and that leaflet is the authority on storage timing, not anything you read online.

Your injection sites are the abdomen, the front of your thigh, or the outer upper arm. Rotate between them weekly so the same patch of skin gets a rest. If you're unsure about technique, our guide to beginning Wegovy walks through the injection process in plain terms. The needle is short and fine; the majority of people who were anxious about self-injecting beforehand find it far less dramatic than they anticipated.

One practical habit worth building from day one: keep a brief note (on your phone or a pad) of the date, which site you injected, and how you felt over the following 48 hours. It is the kind of record your prescriber will ask about at your first review, and having it makes that conversation much quicker.

What the first few weeks on Wegovy actually feel like

The 0.25 mg starting dose exists to help your system adjust, not to produce the weight-loss results you read about in trials. Most people notice relatively little appetite change at this stage. What they do notice, often, is nausea, particularly in the 12–24 hours after the injection. It is rarely severe at the lower dose, but it is common enough that planning your injection for a quieter part of the week makes sense. Some people find an evening injection works well because any queasiness passes overnight.

Nausea, loose stools, constipation, and indigestion are the most frequently reported effects, especially at the start of treatment and again after each dose increase. The NHS semaglutide medicines page lists these in full alongside rarer effects worth being aware of. The GI symptoms typically settle within one to two weeks at a given dose level; they tend to return briefly when the dose steps up, then settle again. Eating smaller meals, avoiding very fatty or heavily spiced food in the days around your injection, and keeping well hydrated all reduce the severity for most people.

Fatigue and headache appear in some people during the first few weeks. They are generally short-lived. If you are experiencing symptoms that feel disproportionate or are not improving after two weeks at a dose, contact your prescriber rather than pushing through. Our guide to things worth knowing when starting Wegovy covers what to expect in more detail, including how to tell the difference between effects that are normal and those that need attention.

When to get medical help, and what to watch for

Most side effects on Wegovy are uncomfortable rather than dangerous. A small number are signals to seek prompt medical attention. Severe stomach pain that radiates toward the back, with or without vomiting and not easing with ordinary measures, needs urgent assessment, this is the presentation associated with acute pancreatitis, which the MHRA has confirmed as an infrequent but serious risk with GLP-1 medicines. Symptoms of a gallbladder problem (severe pain in the upper right abdomen, sometimes with fever or yellowing of the skin) also warrant same-day contact with a doctor.

Signs of a serious allergic reaction (swelling of the face, throat tightening, difficulty breathing) require emergency services. These are rare but worth knowing before they happen rather than after.

For anything less acute, our aftercare team is available seven days a week. If something does not feel right and you cannot reach us, NHS 111 is the appropriate route. Report any suspected side effects, however minor, through the MHRA Yellow Card scheme, it helps regulators monitor newly approved medicines.

Pregnancy, breastfeeding, and actively trying to conceive are all situations where Wegovy is not recommended. Under-18s are outside the licensed age range. Both points are discussed at consultation, but they are worth raising directly with your prescriber if your circumstances change while you are on treatment.

The longer picture: what starting Wegovy is actually beginning

The STEP 1 trial, published in the New England Journal of Medicine, found an average body-weight reduction of around 15% over 68 weeks at the 2.4 mg maintenance dose, a figure that reflects months of gradual dose increases, consistent injections, and lifestyle changes alongside the medicine. If you want a practical checklist before your first pen arrives, our guide to what to do when starting Wegovy sets out the steps to take so you feel prepared from day one. The medicine reduces appetite; the rest still involves building the habits that support sustained weight management, and our guide to what to know when taking Wegovy is a useful reference to keep coming back to as your treatment progresses.

For context on how much treatment costs privately and what that price includes, our guide to where to get Wegovy in the UK covers the licensed options. Wegovy is a prescription medicine and cannot be legally supplied without one; understanding the access routes before you start helps you plan your repeat prescriptions rather than scrambling when a pen runs low.

If you have not yet started and are still exploring your options, the Wegovy overview page covers the full picture from eligibility to what the NHS route involves. Our weight-loss treatment page sets Wegovy alongside the other licensed options if you are still deciding. And if you are ready to speak to a prescriber, a free consultation with our clinical team is the right next step.