Using a Weight Loss Injection: What to Know About Sites and Rotation

Mounjaro and Wegovy are both administered as a once-weekly subcutaneous injection — meaning the needle goes into the fatty tissue just beneath the skin, not into a muscle or vein. The most commonly used sites are:

• Abdomen — the area around the stomach, avoiding the area immediately around the navel
• Front of the thigh — the outer or upper portion of either thigh
• Upper arm — the outer, fleshy area of the upper arm (often easier with assistance)

Rotating between these sites — rather than injecting into exactly the same spot each time — is generally recommended because repeated injections into one area can affect the tissue beneath the skin over time, which may change how the medicine is absorbed. Your prescriber or doctor will have given you guidance on technique; always follow their instructions and the patient information leaflet that came with your pen.

It is worth noting that the best site for you may depend on factors your prescriber knows about, so if you are unsure, asking at your next appointment is a good idea. For a broader overview of how these medicines work and what to expect, see our guide to weight loss injections. You may also find it useful to read about what a weight loss injection involves if you are early in your journey.

One practical question many people have is whether certain sites absorb the medicine faster or more consistently. According to information aligned with the electronic Medicines Compendium (eMC) product information, the abdomen is one of the most commonly studied sites, but all three approved sites are considered suitable — rotate as instructed and note any site reactions when they occur.

Keeping track of which site you used last week is surprisingly easy to forget — especially across months of weekly injections. GLP Trackr's injection-site tracking feature is built exactly for this: each time you log a dose, you record the site you used, and the app keeps a rotation history so it can suggest where to inject next. There is no guesswork and no relying on memory.

Alongside site logging, the app lets you record your dose strength and the date and time of each injection, so you always have a clear, timestamped picture of your treatment history. Dose reminders mean a weekly injection is much less likely to be overlooked — particularly useful when life gets busy.

If you notice any injection-site reactions — redness, swelling, or discomfort — you can log those too and track whether they are tied to a particular site or pattern over time. That kind of record can be genuinely useful to bring to your prescriber at a review appointment.

Always follow the guidance your prescriber or doctor has given you about how and where to inject. If you experience a reaction that is severe, persistent, or concerns you, contact your healthcare professional promptly — the app supports your tracking but is not a substitute for clinical advice.

You might also want to explore our pages on choosing the right approach to your weight loss injection and understanding your prescription for more context on managing your treatment. For the full picture on tracking your journey, the weight loss injections hub brings it all together.

Ready to take the guesswork out of rotation? GLP Trackr is free to try for 7 days — download it on the App Store or Google Play and let the app handle the tracking from your very first logged dose.