If a Mounjaro® pen is difficult to use or does not release medication as expected, follow the troubleshooting steps below to check whether the Mounjaro® pen is functioning correctly.
Overview
This article explains:
Common reasons a Mounjaro® pen may not work properly
Step-by-step troubleshooting and priming guidance
How needle use, technique, and storage affect pen function
When a Mounjaro® pen may need replacement
Use this guide before attempting another Mounjaro® injection.
Common signs of a Mounjaro® pen issue
A Mounjaro® pen may require troubleshooting if:
The dose knob is hard to press
No medicine droplet appears during priming
Medication does not flow through the needle
The pen has been stored incorrectly or damaged
Step-by-step troubleshooting for a hard-to-press dose knob
Follow these steps using a new needle:
Attach a new disposable needle to the Mounjaro® pen.
Remove the paper tab from the outer needle shield.
Push the capped needle straight onto the pen and twist until secure.
Remove the outer needle cap and keep it for disposal.
Remove and discard the inner needle shield.
Turn the dose knob back to “0.”
Slowly turn the dose knob until 2 clicks are heard and the extended line appears in the dose window (prime position).
Hold the Mounjaro® pen upright with the needle pointing upward and gently tap the cartridge holder to move air bubbles to the top.
Press the dose knob fully in and hold for 5 seconds to release a small amount of medicine into the air.
Confirm the “0” appears in the dose window.
A small droplet at the needle tip indicates successful priming.
A visible stream is not required.
Do not inject into the body during troubleshooting.
If the Mounjaro® pen still does not work
If medication still does not appear after repeating the troubleshooting steps:
The needle may be blocked or damaged
The pen mechanism may be faulty
The pen may have been stored incorrectly
In these situations, the Mounjaro® pen may be unusable and should not be used for injection.
Preventing Mounjaro® pen problems
Injection technique
Prime the Mounjaro® pen before each injection to remove air.
If the dose knob feels stiff, press the knob slowly and steadily.
Correct needle use
Always use a new needle for every Mounjaro® injection.
Ensure the needle is straight, undamaged, and securely attached.
Never press the dose knob without a needle attached, as this can:
Increase pressure inside the cartridge
Cause leakage or medicine loss
Damage the pen mechanism
Blocked or poorly attached needles can make the dose knob difficult to press.
Proper Mounjaro® pen storage
Store the Mounjaro® pen in a clean, dry place within the correct temperature range.
Do not store the pen with a needle attached, as this may cause:
Leakage
Needle blockage
Air entering the pen
Always store the Mounjaro® pen with the pen cap attached.
Exposure to dust, lint, food, or liquid may damage the mechanism and make the dose knob hard to press.
If contamination occurs, the pen should be discarded.
Key takeaway
A hard-to-press dose knob is often caused by a blocked or damaged needle or incorrect priming.
Using a new needle and re-priming the Mounjaro® pen resolves many issues.
Incorrect storage, contamination, or mechanical faults may make the pen unusable.
If you still need help after reviewing the information above, additional assistance is available.