How to Prime a Mounjaro Pen Before Your Injection

The Mounjaro injector pen is pre-filled with tirzepatide solution. Priming serves two purposes: it clears any air from the needle and confirms the pen is functioning correctly before the dose is delivered. Without priming, air in the needle path could mean you receive less than your intended dose.

Preparing the pen

Before you prime, check that the liquid in the pen window looks clear and colourless. If it appears cloudy, discoloured, or contains visible particles, do not use that pen — contact your prescriber or doctor, or the pharmacy that dispensed it. The pen should also have been stored correctly; check the leaflet that came with your pen for storage guidance, but typically an unopened pen is kept refrigerated and can be kept at room temperature for a limited period once in use. See our separate guide on keeping your pen safe and protected for practical storage tips.

Attaching the needle and priming

Attach a new, sterile needle (supplied separately) by pressing it firmly onto the pen tip and twisting until secure. Remove the outer and inner needle caps and keep the outer cap for safe needle removal later. Turn the dose selector to the prime symbol (a small droplet icon on most KwikPen devices). Hold the pen with the needle pointing upward and press and hold the injection button until you see a drop or stream of liquid at the needle tip — that confirms the pen is primed and ready. If no liquid appears, check the leaflet or contact your prescriber before proceeding.

Common questions about pen setup

A full Mounjaro pen contains multiple doses — the exact number depends on the strength of the pen (for example, a 5 mg pen or a 12.5 mg pen). Contrary to a popular idea sometimes called the "golden dose", the pen does not contain extra hidden doses beyond what is stated on the label. If the pen feels stuck or the dial will not move, do not force it — read the troubleshooting section of your leaflet or see our guide on what to do if your Mounjaro pen jams. Some pens have a small reset or safety button; refer to your own pen's leaflet for confirmation of features specific to your device.

If you notice the pen still has liquid in it after the dose counter reaches zero, that is normal — a small amount of liquid remains in all pre-filled pens as part of the design and does not represent an additional dose. Do not attempt to extract it. When you are ready to think about ordering your next supply, plan ahead so you are not left without your medication; your prescriber or dispensing pharmacy can advise on timing.

For a broader overview of how the pen works and what to expect, visit our guide on the Mounjaro pen, or explore the full Mounjaro information hub for more topics.

Keeping track of exactly when you injected, which pen you used, and which site you chose is easy to forget over a weekly schedule — and that is where GLP Trackr is most useful for this part of your journey.

The app's dose logging feature lets you record each injection as it happens: the date, time, and dose strength all stored in one place, so you always know when your last shot was and when the next one is due. Gentle dose reminders mean a weekly injection is far less likely to slip your mind.

GLP Trackr also tracks injection site rotation — log whether you injected in the abdomen, thigh, or upper arm, and the app keeps a history so you can vary the site each week without having to remember manually. Rotating sites is commonly recommended to look after the injection area over time.

If you ever feel uncertain about how your pen is working or want to keep a record to discuss with your prescriber, logging your injections consistently gives you a clear, dated history to refer back to. GLP Trackr is a tracking tool, not a medical service — any concerns about your pen, dose, or injection should always be raised with your prescriber or doctor.

Ready to stay on top of every dose? Download GLP Trackr on the App Store or Google Play and start a free 7-day trial — your injection history, site rotation, and weekly reminders all in one place.