Weight Loss Injections: A Guide for People Already on Treatment

Mounjaro and Wegovy are both prescription-only, once-weekly subcutaneous injections — meaning they are delivered just beneath the skin, not into a muscle or vein. According to information in the electronic Medicines Compendium, the three most commonly used injection sites are the abdomen, the front of the thigh, and the upper arm. Each is considered suitable, and your prescriber or the patient information leaflet that came with your pen will confirm which sites are appropriate for you.

Why Rotation Matters

Rotating between different sites — and between different areas within each site — helps prevent localised skin reactions such as hardening or tenderness. Repeatedly injecting into exactly the same spot can affect how the medicine is absorbed over time. A simple rule of thumb is to move at least a few centimetres from your last injection point each week, though always follow the specific guidance provided by your prescriber or doctor.

Injection Timing and Schedule

Both medicines are typically taken once a week, on the same day each week. Your prescriber sets the schedule and any dose changes — those decisions always belong with them, not with you alone. If you are unsure about your current schedule, your patient information leaflet or a quick call to your prescriber is the right first step.

Because these medicines are prescription-only, they are obtained through a registered pharmacy on the basis of a valid prescription. If you are researching weight loss injections more broadly, our overview guide covers the landscape in more detail. You may also find it useful to read about the risks associated with weight loss injections and what to discuss with your healthcare team before and during treatment.

For those curious about how different injectable treatments compare, our pages on weight loss injections beginning with T and those beginning with S provide factual, neutral overviews. If you have questions about using an injection alongside a specific health condition, see our guide on weight loss injections and type 2 diabetes.

Staying consistent with a weekly injection schedule is easier when you have a reliable record — and that is exactly where GLP Trackr is built to help. The app's injection-site tracking and rotation feature lets you log each site you use, so you always know where you injected last and where to go next. Rather than trying to remember or keep a paper note, the app builds up your rotation history automatically and can suggest your next site based on what you have already logged.

Alongside site tracking, dose reminders mean your weekly injection day does not sneak up on you. You can log the dose strength and date of every injection, giving you a clear, time-stamped record of your entire treatment history — useful if you ever want to share a summary with your prescriber at an appointment. The doctor report feature compiles your logged data into a clear summary you can bring to your next consultation.

If you notice anything at the injection site — redness, tenderness, or any other reaction — you can log it in the side-effect tracker and see whether a pattern emerges over time. Anything persistent or concerning should always be discussed with your prescriber or doctor promptly; GLP Trackr is a companion for recording and reflecting, not a substitute for professional advice.

You can also explore our page on what a weight loss injection course involves and read more about daily injection options for broader context on different treatment schedules.

Ready to take the guesswork out of rotation and never lose track of an injection again? GLP Trackr is available free on the App Store and Google Play — give it a try with a 7-day free trial and see how it fits into your weekly routine.