Using a Wegovy pen for your first injection: what the guidance actually says

What the trial protocol tells us about first-dose preparation

The STEP 1 trial, published in the New England Journal of Medicine, enrolled adults who began semaglutide at exactly the dose you will start: 0.25 mg once weekly, titrated upward every four weeks under clinical oversight. That controlled, stepped approach was not incidental — it was the designed mechanism for keeping gastrointestinal side effects manageable while the body adjusted. Your first injection replicates it. Preparation matters, and the official guidance is reassuringly specific.

Take the pen from the fridge and let it sit at room temperature for around 30 minutes before injecting; a cold pen can make the injection more uncomfortable than it needs to be. Check the liquid through the viewing window: it should be clear or almost clear and colourless to slightly yellow. A cloudy, discoloured or particulate solution should not be used. Remove the pen cap only when you are ready. Many people assume the pen needs priming before each use, as syringes do. It does not, and if you want a full walkthrough of the device before you begin, our guide to getting your Wegovy pen ready for first use covers every step in detail.

Wash your hands thoroughly, then clean the chosen skin site with an alcohol swab and let it dry completely before injecting. Wet skin can sting.

The injection itself: technique that reduces discomfort

Pinch a fold of skin lightly between your fingers and hold the pen against the skin at a 90-degree angle. Press the injection button firmly until it clicks, then hold the pen in place for at least six seconds, this allows the full dose to be delivered and helps prevent leakage back through the needle track. Release the button, then lift the pen straight away from the skin.

The needle is fine and short; most people describe the sensation as a mild scratch rather than a sting. If you feel a sharp pinch, the site may have been tensed, relaxing the muscle in the thigh, for instance, makes a real difference. Rotate injection sites week to week, and within each site avoid exactly the same spot as the week before; this reduces the small risk of lipohypertrophy, a localised thickening of the fat layer that can affect absorption. For a step-by-step guide to your first injection of Wegovy, including site selection and technique tips, we have a dedicated page that walks you through the process.

After the injection, apply gentle pressure with a dry swab if there is any minor bleeding, but do not rub the area. Do not recap the needle. The used pen goes straight into a dedicated sharps bin; standard household bins are not safe for used medical sharps, and NHS guidance asks that you return your full sharps bin to a pharmacy or household waste site that accepts them.

Storing Wegovy correctly after your first injection

Because each pen contains one dose, storage after first use is straightforward: the pen is finished and should be discarded. Future pens stay in the fridge until needed. The Patient Information Leaflet included with your pack gives the exact number of hours a pen may safely be kept at room temperature if refrigeration is temporarily unavailable, refer to that document rather than any general estimate, because the window is specific to this formulation. Storing Wegovy correctly matters for both safety and effectiveness; temperature excursions can degrade the active medicine without any visible sign. If you would also like a complete overview of how to use Wegovy for the first time, covering everything from unpacking the pen to completing the injection, that guide brings all of the key steps together in one place.

Travel, GP appointments and gym bags all create storage challenges. Plan ahead: an insulated cool bag with a gel ice pack (not direct ice) works well for short journeys. Your prescriber can advise on longer travel periods during a clinical review.

Side effects to watch for after the first dose, and when to seek help

Nausea is the most commonly reported effect after a first injection, typically mild, appearing within hours and easing over a few days. Diarrhoea, constipation and a reduced appetite are also common at the start. These are well-documented in the trial data and tend to lessen as the body settles at the starter dose. Eating a smaller, lower-fat meal on injection day can help.

Contact a doctor promptly if you experience severe or persistent stomach pain, particularly pain that radiates to the back, this is a symptom the MHRA flagged in a January 2026 Drug Safety Update as a warning sign for acute pancreatitis, an uncommon but serious reaction. Symptoms of a severe allergic reaction (widespread rash, swelling, breathing difficulty) also require urgent medical attention. If you ever want to report a side effect yourself, the MHRA Yellow Card scheme is open to patients as well as clinicians.

You can read a broader overview of the medicine and the treatment journey on the Wegovy treatment page, or explore all weight-loss options we support if you are still deciding which route suits you. Semaglutide (Wegovy) is sometimes confused with Ozempic, which contains the same active ingredient but holds a different UK licence, one worth understanding clearly before starting. Our clinical team reviews every patient individually; a prescriber, not software, reads your consultation answers the same day.