Weight Loss Jabs: What to Know About Mounjaro Injections

Mounjaro belongs to a class of weight loss jabs known as GLP-1 receptor agonists — though more precisely it is a dual GIP and GLP-1 receptor agonist, which distinguishes it from some other injectable medicines in this space. It is supplied as a pre-filled pen and is administered once a week, with the dose and any adjustments determined entirely by your prescriber or doctor.

Common injection sites

The three sites most commonly used for subcutaneous injections of this type are:

• Abdomen — the area around the stomach, avoiding the navel
• Upper thigh — the front or outer part of the thigh
• Upper arm — the outer area of the upper arm (often easier with assistance)

Your prescriber or the patient information leaflet that came with your pen will give you specific guidance on technique. The content here is general and informational — any questions about your individual injection method should go to your healthcare professional.

Why injection site rotation matters

Reusing the same spot repeatedly can cause localised changes in the tissue beneath the skin, which may affect how the medicine is absorbed. Rotating between sites — and within each site — is a widely recommended practice for anyone using weekly injectable medicines. Keeping a record of where you last injected makes rotation much easier to stay on top of.

There are several types of weight loss jabs currently available or in development, including semaglutide (Wegovy) and others further along in research pipelines. For a broader look at the injectable options people are prescribed, see our guide to weight loss jabs or the weight loss injections overview.

If you have seen news coverage about newer jabs such as retatrutide, it is worth knowing that only medicines prescribed to you by your own clinician are relevant to your current treatment. Any questions about different weight loss jabs or switching should be directed to your prescriber.

Keeping track of which site you used last — and when you last injected — is exactly the kind of small but meaningful detail that is easy to forget over weeks and months of treatment. GLP Trackr's injection-site tracking logs each site you use and automatically suggests your next rotation, so you never have to rely on memory alone.

Alongside site tracking, the app logs each dose and the date and time of every injection, giving you a clear record of your weekly schedule. If a dose reminder would help you stay consistent, you can set one so your weekly jab day is never quietly missed.

All of this logging also has a practical benefit beyond routine: if you ever want to discuss your injection history with your prescriber — for example, if you notice localised reactions or have questions about your schedule — you have a ready-made record to bring to that conversation.

For context on what to expect around concerns sometimes raised about weight loss jabs — including questions about safety and side effects — our page on new fears around weight loss jabs covers some of the topics people commonly search. You can also find information about access through different routes on our weight loss jabs and pharmacy access page.

Any concerns about your injection — whether that is a site reaction, a question about your pen, or anything that feels unusual — should be raised with your prescriber or doctor promptly. GLP Trackr records what you experience so you can have that conversation with the full picture; it is not a substitute for their guidance. If you believe you have experienced a side effect, you can report it to your national pharmacovigilance scheme (such as the UK's Yellow Card scheme) and discuss it with your healthcare professional.

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