How to Take Mounjaro: A Practical Guide for People Already Prescribed It

Mounjaro is injected once a week, on the same day each week, using a pre-filled KwikPen device. According to the electronic Medicines Compendium (eMC), the three recommended injection sites are the abdomen, the front of the thigh, or the upper arm. The injection goes into the fatty tissue just beneath the skin — this is called a subcutaneous injection.

Rotating Your Injection Site

Rotating where you inject each week is important. Using exactly the same spot repeatedly can cause changes to the tissue under the skin, which may affect how well the medicine is absorbed. A simple rule many people follow: move to a different area each week, and avoid injecting into skin that is sore, bruised, or irritated. Your prescriber or the patient information leaflet that came with your pen will have guidance specific to your medicine.

The Starting Dose and How It Changes

Most people begin at 2.5 mg once weekly. The dose is typically increased gradually — at intervals decided by your prescriber — up to a maintenance dose that suits you individually. This step-up approach is designed to help your body adjust. Any decisions about moving to a higher strength, or staying at your current dose longer, belong entirely with your prescriber or doctor. For a broader look at how tirzepatide works in the body, see our guide on how Mounjaro works.

Choosing Your Injection Day

Pick a day of the week that fits your routine and try to stick to it. If you need to shift your injection day, your prescriber can advise on how to manage this safely — it is not a decision to make without guidance. You can also explore when to take Mounjaro for more on timing and day selection. If you are curious about how other GLP-1 medicines are taken, our overview of how GLP-1 medicines are taken covers the broader picture, and there is a dedicated page on how to take Wegovy for those also considering semaglutide.

Before You Inject

Check the expiry date and inspect the liquid in the pen before use — it should be clear and colourless to slightly yellow. Always check the patient information leaflet that came with your pen for storage instructions, as specific guidance on refrigeration and how long a pen can be kept at room temperature varies by product. When in doubt, refer to the leaflet or ask your pharmacist.

Mounjaro is a prescription-only medicine. For factual information on side effects that are commonly reported, understanding your GLP-1 treatment form can also provide useful context on different administration routes.

Staying consistent with a once-weekly injection schedule is straightforward in principle, but easy to lose track of in practice — especially as your dose strength changes over time. GLP Trackr's dose logging feature lets you record each injection the moment you take it: the date, dose strength, and which site you used. That record is always there when you need it.

The injection-site tracking feature goes a step further: it keeps a history of your rotation and can suggest which site is next, so you never have to try to remember whether you used the left or right side of your abdomen last week.

If you ever miss a dose or have a question about your schedule, the app lets you log that too — giving you a clear, timestamped record to bring to your next appointment. GLP Trackr is a tracking and journaling tool; it does not give dosing instructions or replace the advice of your prescriber or doctor. Any decision about your dose — including what to do if you miss an injection — should always be made with your healthcare professional.

If you experience side effects you want to keep track of, such as nausea or injection-site reactions, you can log those alongside your doses so you have a full picture to discuss at your next consultation. Your prescriber knows your full history and is the right person to advise on any symptoms that concern you. Any severe, persistent, or worrying symptoms should be reported to your healthcare professional promptly, and to your national reporting scheme (such as the UK's Yellow Card scheme).

Log your doses, track your sites, and keep your weekly schedule on track — download GLP Trackr free from the App Store or Google Play and start a 7-day trial at no cost.