What Does Mounjaro Look Like?

Each Mounjaro (tirzepatide) pen is a small, pre-filled autoinjector designed for once-weekly subcutaneous injection. The device has a protective needle cap at one end and a viewing window in the body of the pen so you can see the medicine inside before use. The liquid should appear clear and colourless to slightly yellow — if it looks cloudy, discoloured, or contains visible particles, check the patient information leaflet that came with your pen and contact your prescriber or pharmacist before using it.

Colour-coding by dose strength

Each dose strength has its own distinct label colour, making it easier to confirm you have the right pen before injecting. The colour on the label corresponds to the strength — for example, the 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg pens are each differentiated visually. Always check the strength printed on the label and confirm it matches what your prescriber has told you to use. If you are unsure which strength you have been prescribed, your prescriber or doctor is the right person to ask — never adjust based on appearance alone.

How the pen works

The autoinjector is designed so that when the cap is removed and the pen is pressed firmly against the skin, the injection process is initiated with the press of a button. The needle is concealed inside the device, which many people find less daunting than a traditional syringe. After the injection is complete, the pen automatically shields the needle. Each pen is single-use only and should be disposed of safely in a sharps bin — check guidance from your prescriber or local waste service on how to dispose of used pens in your area.

Storage

Check the leaflet that came with your pen, but pens are typically stored in a refrigerator before first use. Once removed from the fridge, the pen can generally be kept at room temperature for a limited period — your patient information leaflet or the electronic Medicines Compendium (eMC) will give you the exact guidance for your specific product. Never freeze the pen, and keep it away from direct sunlight.

If you want to understand more about how tirzepatide works once it is inside the body, see our guide to what Mounjaro does to your body, or explore what Mounjaro does in more detail.

One practical challenge on a weekly injection routine is staying on top of which pen you used, when you used it, and where you injected. GLP Trackr's dose logging feature lets you record each injection — including the date, time, and dose strength — so you always have a clear record of your treatment history in one place.

Alongside dose logging, the app's injection-site tracking helps you rotate sites systematically. You log where you injected (abdomen, thigh, or upper arm), and the app keeps a rotation history so you can avoid reusing the same spot too soon — something your prescriber may have advised to reduce the chance of localised reactions. For a broader understanding of the mechanism behind tirzepatide, our overview of how Mounjaro works and our page on what GLP-1 does in the body give useful context.

If you ever notice anything unexpected about your pen — such as unusual appearance of the liquid, damage to the device, or uncertainty about the dose — always follow the guidance of your prescriber or doctor before proceeding. GLP Trackr helps you keep a record of these observations so you can raise them clearly at your next appointment; it is not a substitute for professional advice.

Ready to bring some order to your weekly routine? Download GLP Trackr on the App Store or Google Play and explore it free for 7 days — your injection log and site rotation history will be waiting every time you pick up your pen.