The Mounjaro Pen: Sizes, Checks, and How to Use It Confidently

Mounjaro pens are available in several dose strengths. According to the electronic Medicines Compendium, the strengths commonly referenced are 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg — for example, a 2.5 mg pen is typically the starting strength, and a 7.5 mg pen represents a mid-titration stage. Your prescriber decides which strength is appropriate for you at each stage; dose changes are never a self-directed decision.

Before you inject: what to check

• Inspect the solution. The liquid in a Mounjaro pen should be clear and colourless to slightly yellow. A cloudy Mounjaro pen, or one containing visible particles, should not be used — contact your prescriber or pharmacist and refer to the patient information leaflet that came with your pen.
• Check the expiry and storage. Pens should be stored as directed in your leaflet (typically refrigerated before first use). Check the leaflet for precise timings rather than relying on memory, as storage guidance is product-specific.
• Priming. The Mounjaro pen does not require the same priming steps as some other injectable devices, but you should always read the instructions in your leaflet carefully before your first use. For a step-by-step walkthrough, see our guide on how to prime your Mounjaro pen.

Pen problems to know about

If your pen feels stiff, will not click, or the mechanism does not move as expected, do not force it. A jammed Mounjaro pen or one that will not twist may have a device fault — contact your pharmacist or prescriber rather than attempting to force the mechanism. Similarly, if you have dropped your Mounjaro pen, inspect it carefully for cracks or damage and check the solution before use; if in doubt, seek advice from your pharmacist.

Checking the pen is finished

A finished Mounjaro pen will typically show a visual indicator that the full dose has been delivered — check your leaflet for the specific confirmation window on your device. If you are unsure whether your dose was fully delivered, do not re-inject; contact your prescriber or pharmacist for guidance. For questions about how many clicks to expect during an injection, our dedicated page explains what to look and listen for.

Safe disposal

Used Mounjaro pens must be disposed of safely. Place used pens in an approved sharps container and follow your local authority's or healthcare provider's guidance on sharps disposal. Do not place pens in general household waste. Your pharmacist can advise on local disposal options.

Carrying and storing your pen

If you travel or want to keep your pen protected between uses, a Mounjaro pen case or holder can help prevent accidental damage. Always store your pen according to the instructions in your leaflet regardless of the case you use.

One of the easiest things to lose track of on a weekly injection schedule is exactly when you last injected, which dose strength you used, and which site you chose. GLP Trackr's dose logging feature lets you record each injection — date, time, and dose strength — so you always have a clear history to refer back to or share with your prescriber.

Beyond the shot itself, the app's injection-site tracking and rotation tool logs where on your body each dose was given (abdomen, thigh, or upper arm) and suggests your next site automatically, taking the guesswork out of rotation. If you ever experience a reaction at a site or notice a pattern in how different locations feel, the side-effect tracker lets you log that alongside your injection record — useful context to bring to your next appointment.

Wherever you are in your Mounjaro journey, having one clear record means no second-guessing. You can find broader guidance on managing your Mounjaro experience in our complete Mounjaro guide.

GLP Trackr is a tracking and journaling app — it is not a substitute for the advice of your prescriber or pharmacist. If your pen appears faulty, the solution looks abnormal, or you have any concerns about your device or dose, contact your healthcare professional. Any decision about your dose belongs with your prescriber.

Ready to log your next shot and keep your full injection history in one place? Download GLP Trackr on the App Store or Google Play and start your free 7-day trial today.