Mounjaro Injection Instructions: A Practical Guide for People Already Prescribed It

Mounjaro is given as a subcutaneous injection — meaning just under the skin — once a week. According to the electronic Medicines Compendium (eMC), the three commonly used areas are the abdomen (stomach area, avoiding the navel), the front of the thigh, and the upper arm. Your prescriber or the patient information leaflet (PIL) that came with your pen is the definitive guide for your individual technique — always refer to those for step-by-step clinical instruction.

Why Rotation Matters

Injecting into the same spot repeatedly can cause changes to the skin and tissue under it, which may affect how the medicine is absorbed. Rotating your site with each weekly dose — for example, moving from the left abdomen one week to the right thigh the next — helps keep tissue in good condition over time. Many people find it useful to have a simple system for remembering which site they used last.

Keeping Track of Your Sites

This is where a consistent logging habit pays off. If you are unsure which site you used for your last dose, it is easy to default to the same spot out of habit. Keeping a record — even a simple one — means you always know where your last injection went and where to go next. For more detail on the injection itself and what to expect, see our pages on using your Mounjaro pen and common injection questions answered. If you want to understand how dose strengths relate to your injection schedule, Mounjaro dose stages explained covers that in detail.

A Note on Technique

The precise clinical steps — how to prepare the pen, the angle of insertion, what to do if you see blood — are set out in the PIL and should be discussed with your prescriber or pharmacist. Content here is informational and is not a substitute for that guidance.

The single most useful feature for injection days is GLP Trackr's injection-site tracking and rotation tool. Each time you log a dose, you record the site you used — abdomen, thigh, or upper arm, left or right — and the app keeps a history of your rotation. Rather than trying to remember from week to week, you can simply check the app to see where you injected last and where to go next.

Alongside site tracking, the app logs the date, time, and dose strength of every injection in one place. This creates a clear record you can bring to your next prescriber appointment — particularly useful if you want to discuss how you have been getting on or if anything has felt different at a particular site. GLP Trackr also includes gentle dose reminders so a weekly injection is less likely to slip your mind.

Staying consistent with a once-weekly injection schedule over months takes more organisation than it might seem at first. Having that record already built up — rather than trying to reconstruct it from memory — makes conversations with your healthcare team much more straightforward.

For a broader look at the injection side of your GLP-1 journey, visit our weight loss injections guide.

Important: any concerns about your injection technique, site reactions, or how to use your pen should be discussed with your prescriber or pharmacist — they know your full history and can give advice specific to you. If you experience a severe or persistent reaction at an injection site, contact your healthcare professional promptly. GLP Trackr helps you record and organise your injection history; it is not a substitute for clinical guidance.

Ready to bring some order to your weekly injection routine? GLP Trackr's site-rotation tracker and dose log are free to try — available on the App Store and Google Play with a 7-day free trial. No pen, no reminder, no rotation missed.