How Mounjaro Pens Work and What to Expect
Each Mounjaro pen contains a single pre-measured dose of tirzepatide. The available dose strengths commonly referenced are 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg — your prescriber will decide which strength is right for you at each stage of your treatment. Because Mounjaro is a once-weekly injection, most people use one pen per week.
How many pens do you receive?
In most cases, prescriptions are issued in a supply covering several weeks — commonly four pens for a monthly supply, though the exact quantity depends on what your prescriber has arranged and how your local pharmacy or dispensing service packages them. Always check your prescription paperwork or speak to your pharmacist if you are unsure how many pens you should have.
Storing your pens
Mounjaro pens should be stored in a refrigerator before first use. Once removed from the fridge, they can generally be kept at room temperature for a limited period — but rather than relying on a single recalled figure, check the patient information leaflet that came with your pens or visit the electronic Medicines Compendium (eMC) for the most up-to-date storage guidance specific to your pen's batch. Pens should never be frozen, and you should keep them away from direct sunlight and heat.
Disposing of used pens safely
Used Mounjaro pens contain a needle and must be disposed of in a sharps container — never placed loose in household waste or recycling. If you are unsure how to access a sharps disposal service, your prescriber, pharmacist, or local waste authority can advise. For a detailed guide, see our page on disposing of Mounjaro pens safely. If you are travelling with your pens, it is worth planning ahead — our guide to travel cases for Mounjaro pens covers what to look for in a suitable carry solution.
Mounjaro uses the same general injection approach as other once-weekly GLP-1 medicines. If you are curious how Mounjaro pens compare to those used with Wegovy (semaglutide), our overview of Wegovy pens covers the key differences. For a broader look at everything related to Mounjaro, visit our complete Mounjaro guide.
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Keeping Track of Your Pens with GLP Trackr
One of the most practical things you can do on a weekly injection schedule is log each dose as soon as you take it. GLP Trackr's dose logging feature lets you record the date, time, and strength of every injection, so you always have a clear picture of where you are in your treatment — particularly useful if your dose has recently changed or you are unsure whether you took your last pen on the right day.
The app also tracks injection-site rotation. You can log which site you used — abdomen, thigh, or upper arm — and GLP Trackr will suggest where to inject next time, helping you avoid reusing the same spot too frequently. And if you ever experience side effects after a particular pen or dose, the side-effect tracker lets you note what you felt and when, building a record you can bring to your next prescriber appointment.
If you ever miss a dose or are unsure about your schedule, log it in the app and raise it with your prescriber or doctor at your earliest opportunity — dose decisions should always be made with their guidance, not independently.
Give GLP Trackr a try — it's available free on the App Store and Google Play, with a 7-day free trial so you can see how it fits into your weekly routine before committing.
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Beautiful, easy-to-read charts show your weight loss trajectory, weekly nutrition trends, medication responses, and wellbeing scores over time — turning raw data into genuine insights.
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Log walks, workouts, and movement with activity targets that flex with your energy levels. On lower-energy dose days, gentler targets keep you moving without burning out.
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Frequently asked questions.
Because Mounjaro is a once-weekly injection, most people use one pen per week — typically four pens for a standard monthly supply. The exact quantity depends on your prescription and how your pharmacy dispenses it, so check with your prescriber or pharmacist if you are unsure.
Mounjaro pens are available in 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg strengths. Your prescriber decides which strength is appropriate for you and when any adjustment should be made — dose decisions are not something to change without their guidance.
Mounjaro pens should be kept in a refrigerator before first use. They can generally be stored at room temperature for a limited period after removal — check the patient information leaflet or the electronic Medicines Compendium (eMC) for the specific timeframe. Never freeze them or expose them to direct heat or sunlight.
Used pens contain a needle and must be placed in an approved sharps container — never loose in household waste. Your pharmacist or local waste authority can advise on sharps disposal services available in your area. Never attempt to recap or re-use a pen.
Yes. GLP Trackr lets you log each injection with the date, time, dose strength, and injection site. This creates an accurate record of every pen you have used, which is helpful for staying on schedule and for discussing your progress with your prescriber.