GLP-1 Injections: What You Need to Know About Sites, Rotation and Staying on Track

GLP-1 receptor agonist medicines such as Mounjaro and Wegovy are injected into subcutaneous fat — the fatty tissue just beneath the skin. The three sites most commonly used are the abdomen (avoiding the area immediately around the navel), the front or outer thigh, and the back of the upper arm. Your prescriber or doctor will confirm which sites are suitable for you personally.

Why rotating sites is recommended

Using the same spot repeatedly can cause lipohypertrophy — a build-up of fatty or scar tissue beneath the skin. This can affect how consistently the medicine is absorbed. Rotating between sites, and moving within each site from one injection to the next, helps the skin recover and supports more reliable absorption. Most patient information leaflets recommend leaving a reasonable gap between injection points — check the leaflet that came with your pen for the specific guidance, as this can vary by product.

Keeping a clear injection record

Because GLP-1 injections happen once a week, it can be surprisingly easy to lose track of which site you used last — especially across a busy week. Keeping a simple log of date, dose strength, and site takes only seconds and creates a useful reference for your next injection. For more on the wider topic of weight-loss injections and how they work, see our guide to using weight-loss injections safely and effectively. You can also read more about how GLP-1 injections work in practice or explore the role of GLP-1 injection in a weight-loss journey.

If you notice anything unusual at an injection site — persistent redness, swelling, pain, or a lump that does not resolve — let your prescriber or doctor know. Any side effects you consider serious should also be reported to your healthcare professional and, where relevant, to your national reporting scheme (such as the UK's Yellow Card scheme).

The most useful starting point in GLP Trackr for anyone on a weekly injection is the injection-site tracker. Each time you inject, you log the site used — abdomen, thigh, or upper arm — and the app keeps a rotation history so it can suggest your next site automatically. There's no need to remember what you did last week; the record is always there.

Alongside site tracking, dose logging lets you record the exact dose strength and date of each injection, giving you a clear, timestamped history of your treatment. This comes into its own at prescriber appointments, where a complete injection log is far more useful than trying to recall details from memory. The app's dose reminders mean a weekly injection is much harder to forget — a gentle nudge at the time you choose.

If you want to understand how injection timing or site choices relate to how you feel day to day, all of this data sits alongside your side-effect logs and daily check-ins, so patterns become visible over time. You can explore more about tracking injections for weight loss in our dedicated guide.

GLP Trackr is a tracking and journaling app — it is not a substitute for the clinical guidance of your prescriber or doctor, who should always be your first call for any question about your dose, injection technique, or how the medicine is working for you.

Ready to take the guesswork out of injection rotation? GLP Trackr is available free on the App Store and Google Play, with a 7-day trial to get you started — log your first shot and let the app handle the rotation reminders from there.