Self-Injecting Semaglutide: What You Need to Decide Before You Start

Choosing where on your body to inject

The three licensed sites for semaglutide injection are the abdomen (at least 5 cm from the navel), the front of the thigh, and the upper arm. All three deliver comparable absorption, so the choice is mostly about what you can comfortably reach and hold steady. Most people starting out find the abdomen easiest to see and control, but the thigh is a good alternative if you'd prefer to sit down and stabilise your leg against a chair.

Rotating among sites and within each site is the part many people overlook. Using the same spot repeatedly can cause the skin to thicken or form small lumps under the surface, which slows how the medicine is absorbed and can affect how well it works. A simple habit is to move a few centimetres from the previous spot each week, working around the area systematically. If you're self-injecting semaglutide into the upper arm, you'll need to rest the pen against a firm surface or ask someone to assist, since reaching that site comfortably on your own takes a little practice.

The semaglutide injection guide goes into more detail on site selection and preparation for each location.

Preparing for the injection: the steps that actually matter

A question our prescribers hear most weeks is whether the skin needs to be cleaned first. Cleaning the chosen area with an alcohol swab and letting it dry completely before inserting the pen is good practice — injecting through wet skin can sting more and carries a small contamination risk. Medical-grade alcohol swabs are designed for this and make it easy to build the step into your routine.

Pinching the skin gently before inserting the needle helps to separate the subcutaneous fat layer from the muscle beneath, which is exactly where the medicine needs to go. Once the pen is held flat against the skin at a 90-degree angle, press the button and hold it in place for the count your prescriber or Patient Information Leaflet specifies (usually around five to ten seconds) before withdrawing. Releasing too quickly is the most common reason a small amount of medicine appears on the skin surface after the injection.

Remove the pen cap only immediately before use. Used pens should go straight into a puncture-resistant sharps container rather than a household bin, your local pharmacy or GP surgery can advise on how to dispose of it once the container is full. Full step-by-step technique guidance is also covered in the Wegovy injection technique walkthrough.

Side effects at the injection site and what they tell you

Localised redness, mild bruising, or a small raised area after the injection are common, particularly in the first few weeks. They almost always resolve within a day or two and aren't a sign that something has gone wrong. What you want to avoid is a persistent hard nodule under the skin, which is a marker of lipohypertrophy, the tissue change that develops from repeatedly injecting the same spot. It's painless, which is part of why people don't always notice they're staying in the same location.

Systemic side effects (nausea, constipation, and digestive discomfort) are unrelated to technique and are covered in more detail alongside injection advice. The NHS semaglutide medicines page lists the full side-effect profile and sets out clearly which symptoms need prompt medical attention. For anything at the injection site that looks infected (spreading redness, warmth, swelling) or for an allergic reaction (hives, difficulty breathing, swelling of the face), seek medical help that day rather than waiting for your next appointment.

The cost of treatment is worth understanding before you start, the weight-loss treatments page sets out what's included at every stage, with no hidden fees.

Keeping the pen safe between doses

Semaglutide pens are temperature-sensitive. The pen must be stored in a refrigerator at 2°C to 8°C and kept away from the freezer compartment, a frozen pen cannot be used and must be discarded. If a pen has been left at room temperature, the Patient Information Leaflet specifies the maximum time it remains usable; never assume it's fine without checking. For anything involving a pen that's been exposed to heat, the guide on what to do if Wegovy gets warm covers the decisions you'll face.

NHS England's guidance on weight management injections also notes the importance of telling any healthcare professional (including a dentist or anaesthetist) that you are using semaglutide before any procedure. The medicine slows gastric emptying, which has implications for sedation and anaesthesia that the clinical team needs to plan around.

If you're thinking about starting semaglutide and want a prescriber to assess whether it's right for you, speak to our prescribers through a free consultation.