Weight Loss Injections: What to Know About Mounjaro

Mounjaro is supplied as a pre-filled pen and is injected once a week, on the same day each week. The three commonly used injection sites are the abdomen, the front of the thigh, and the upper arm — each offers a subcutaneous (under-the-skin) layer that allows the medicine to be absorbed steadily.

Why injection-site rotation matters

Rotating between sites — and between different spots within the same site — helps the skin and underlying tissue recover properly. Repeatedly injecting in exactly the same spot can cause localised skin changes over time, which may affect how the medicine is absorbed. Your prescriber or the patient information leaflet (PIL) that came with your pen will give you specific guidance on technique and rotation.

Dose titration is your prescriber's decision

Mounjaro is typically started at a low dose and adjusted over time according to your prescriber's judgement. Commonly referenced strengths include 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg. How quickly — or whether — your dose changes is an individual clinical decision. Never adjust your dose without speaking to your prescriber first.

Commonly reported experiences

Many people on Mounjaro report changes in appetite and a reduced sense of food noise alongside gastrointestinal side effects, particularly in the days following an injection or after a dose increase. These are among the most commonly discussed aspects of the Mounjaro journey — you can read more about weight loss injections generally or explore further detail on the Mounjaro injection experience.

Mounjaro carries a black triangle (▼) designation, meaning it is subject to additional monitoring. Any side effects should be reported to your healthcare professional and to your national reporting scheme (such as the UK's Yellow Card scheme or the equivalent body in your country).

Keeping a clear record of every injection — which site you used, when you injected, and which dose — is one of the most practical things you can do to stay on track. GLP Trackr's injection-site tracking feature logs each site (abdomen, thigh, or arm) and builds up a rotation history, then suggests where your next injection should go. Over weeks, that simple habit can help you avoid overusing any one area.

Alongside site tracking, the app logs your dose strength and the date and time of each injection, so you always have a clear picture of your treatment schedule. Dose reminders mean a weekly shot is less likely to slip your mind — especially useful during the early weeks when the routine is still becoming second nature.

If you want to understand how your injection day relates to how you feel — energy levels, appetite, or side effects — the app's daily check-in and side-effect log let you connect those dots and bring a clear summary to your next prescriber appointment.

For context on what the injection journey typically looks like week to week, the weight loss injections overview is a useful starting point. If you are thinking about the broader costs involved in staying on treatment, see our page on weight loss injection costs and what to consider. And if you are looking for practical support near you, our page on finding Mounjaro support in your area may help.

A note on safety: if you experience severe, persistent, or concerning symptoms at any point during your treatment, contact your healthcare professional promptly. GLP Trackr helps you record what you notice — it is not a substitute for clinical advice, and any questions about your dose or injection technique belong with your prescriber.

Ready to take the guesswork out of injection-site 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 shot.