Troubleshooting a Mounjaro pen that is not working

If your weight loss pen does not seem to be administering any medication, the most common causes are a bent needle, a needle not screwed on straight, or air/pressure in the pen. Working through a short set of checks usually solves the problem. If the pen still does not work after the checks, contact us.

Who this applies to

This article applies to patients using weight loss injection pens (such as Mounjaro). If you are using a different injection device, the troubleshooting steps may differ.

Step 1: check the needle is not bent

Take the needle off its protective paper top and look down it. If the tip is visibly bent or damaged, replace it with a new needle. Each pack includes a spare needle for this reason.

Step 2: check the needle is on straight and firmly attached

Put the needle onto the pen and make sure it is straight, not at an angle. It needs to be firm enough to pierce the cartridge inside the pen, but not over-tightened. If the pen feels stuck or jammed when you try to dial a dose, the needle is usually the problem. It is essential that you do not repeatedly try to force the pen as this will cause further issues. Nothing on the pen should have to be forced for it to be able to function. 

Step 3: look for beading

Beading is the small drop of medication that appears at the tip of the needle when everything is connected properly. If you see beading, the pen is working.

If you do not see beading, try priming the pen with an air shot:

1. Turn the dose dial all the way down to zero (for a Mounjaro pen).
2. Put the needle on the pen.
3. Turn the dial two clicks, this is the first longer line just past zero.
4. Press the button down. This is the air shot and should push a small drop of medication out of the needle. 
5. Hold for 5 seconds.

Common scenarios

• You have screwed on the needle and the pen feels stuck. Check the needle is straight; this is usually the cause.
• You can dial a dose but nothing comes out. Try the air shot and check for beading.
• The pen worked before but is not working now. Try a fresh needle from the spare in the pack.

What to do next

If you have worked through all three steps and the pen is still not working, contact us with your order number, the strength of pen you are using, and a brief description of what is happening. You will need to include photos of the pen and the needle or if possible, a video. If this cannot diagnose the issue, we may be able to send a returns link to investigate further. 

If the pen is received and tested as functional, it will be sent back to you. If it is not for any reason, we will send it to the manufacturer for further investigation and any missed doses will be compensated at the manager's discretion. 

Still need help?

See our Contact us article for the best way to reach our team.