How to take the weight loss injection, step by step

Step 1, before you inject: preparing correctly

Remove your pen from the fridge about 30 minutes before use. Injecting cold medicine straight from the fridge is one of the most common causes of stinging and injection-site discomfort, and it is entirely avoidable. While the pen is warming, wash your hands thoroughly with soap and water.

Check the pen visually. The liquid should be clear or very slightly yellow and free of particles. If it looks cloudy, discoloured or contains floating matter, do not use it, contact your prescriber or pharmacy. Your Mounjaro KwikPen or Wegovy pen will have arrived sealed, in plain unbranded packaging via DPD tracked delivery; if the outer seal is broken on arrival, report that too.

Clean the injection site with an alcohol swab and allow the skin to dry completely before injecting. Injecting through wet skin can introduce bacteria or cause a stinging sensation that puts people off continuing.

Choose your site for this week: abdomen (at least 5 cm from the navel), outer thigh or upper arm. Keep a simple mental or written note of last week's site so you can rotate, the NHS tirzepatide guidance confirms rotation is important for reducing localised reactions.

Step 2, the injection itself

Both the Mounjaro KwikPen and the Wegovy pen are pre-filled and pre-set; you do not draw up a dose or handle a needle directly. Remove the cap. Pinch a fold of skin at the cleaned site if you are using your abdomen or thigh. Hold the pen flat against the skin (do not angle it) and press until you hear or feel the click that signals the injection has started. Keep the pen held firmly in place for the count stated in your Patient Information Leaflet (usually around 10 seconds) to ensure the full dose delivers.

Release the skin fold, then lift the pen away. A small amount of blood or clear fluid at the site is normal. Apply light pressure with a clean cotton pad if needed; do not rub, as this can disperse the medicine unevenly under the skin.

The needle retracts or is covered automatically on both pen types once the injection is complete, reducing accidental needle-stick risk.

Step 3, after the injection: disposal and what to watch for

Used pens are clinical sharps and cannot go in a household bin. Place each used pen into a sharps container immediately after use. When the container is three-quarters full, seal it and return it via your local council's sharps disposal scheme, most local authorities in England have one, and your pharmacy can advise on the nearest point.

Side effects are most noticeable in the days after starting treatment or after a dose increase. Nausea, loose stools, constipation and indigestion are the most frequently reported; they tend to ease as the body adjusts over a few weeks, according to NHS England's guidance on weight management injections. Eating smaller meals, staying well hydrated and avoiding very high-fat or spicy foods in the first weeks helps most people manage.

Seek urgent medical attention if you experience severe, persistent abdominal pain that travels to your back, with or without vomiting. This symptom pattern can indicate pancreatitis, which is a known but infrequent side effect highlighted in a 2026 MHRA Drug Safety Update for GLP-1 medicines. Any suspected side effect can also be reported directly at the MHRA's Yellow Card scheme.

Storing your pens and keeping to the weekly schedule

Unused pens live in the fridge door, the same cool zone where you might keep butter or an open bottle. Keep them away from the back wall where temperatures can drop below 2°C and freeze the medicine, which would render the pen unusable.

The once-weekly schedule works best when you fix a day that suits your week. Many people find a Sunday evening or Monday morning easy to remember; the specific day does not matter, but consistency does. If you have questions about when results typically start to show, or are wondering how long treatment usually continues, those are decisions shaped by how your body responds and reviewed with your prescriber at each repeat, never a fixed rule set in advance.

If you miss a dose, your Patient Information Leaflet gives the exact guidance on how long after your missed day you can still inject. Do not double up. Titration timing (moving from one strength to the next) is your prescriber's call, not something to self-adjust based on forums or general information. The cost of treatment and what's included in a private prescription are covered on our treatment overview page.

If technique is still a concern after reading the leaflet, our prescribers are available for aftercare support seven days a week, and if you are unsure whether you are a suitable candidate for weight loss injections, that page walks through the clinical criteria in plain language. You may also find it useful to read about how to get the weight loss injection prescribed, including what the consultation process involves, or to explore how long you are likely to need to stay on treatment before speaking to your prescriber. Check our FAQs for the fastest way to reach the team, or contact us directly. When you're ready to see whether you're clinically suitable, check your eligibility through a free consultation.