Troubleshooting Pre-Filled Weight Loss Injection Pens
If your Mounjaro or Wegovy pen is causing you issues, don’t worry. Usually, any problems with these pens can be resolved quickly and easily.
Always follow the Instructions for Use that came with your pen (they’re the definitive steps for your specific device). If anything here conflicts with your manufacturer leaflet, use the leaflet.
If you’re ever unsure, pause and contact your prescriber/pharmacy.
⚠️ Safety First ⚠️
Do not use the pen and contact your prescriber/pharmacy urgently if:
the pen is cracked, leaking, dropped hard, or the dose knob/parts are loose or detached
the medicine looks cloudy, has particles, or looks unusual
the pen was frozen or exposed to contamination (dust/food/liquid)
Never:
reuse needles (this increases blockage/infection risk)
leave a needle attached between doses (this can cause leakage/air/contamination)
try to ‘extract extra doses’ from leftover liquid in the pen (this carries a sterility/dosing risk). If you suspect a defective pen, don’t try to salvage medication.
Fix
Problem
Stop (remove pen from skin if already injected).
Replace with a new needle.
Prime (as per leaflet).
Inject with the pen at 90° to the skin, with your thumb centred on the button.
Press slowly and steadily (not a sudden shove).
After the click/activation, hold in place and count slowly to 5 before removing.
If still jammed: the official manufacturer-style guidance is to discard the pen and use a new one, as the mechanism may be clogged or otherwise faulty. If you’re at this stage, contact your prescriber.
Dose knob is hard to press
Pen won’t click
Pen is jammed
For multi-dose pens, it can be normal to see residual liquid even when the pen has delivered its intended number of doses, and the mechanism may lock after the planned doses.
What to do
Don’t try to get a fifth dose from the pen - they are designed to deliver 4 doses only.
Start a new pen for your next scheduled dose.
I’ve done 4 doses, but there’s still liquid and now it won’t dial
Stop (remove pen from skin if already injected).
Replace with a new needle.
Prime (as per leaflet).
Inject with the pen at 90° to the skin, with your thumb centred on the button.
Press slowly and steadily (not a sudden shove).
After the click/activation, hold in place and count slowly to 5 before removing.
Stop and contact your provider if:
you still can’t get a droplet after correct priming, or
you’ve primed many times (over-priming can empty the pen early).
No medicine comes out when I prime
Common causes include:
damage
needle left on during storage
poor needle attachment.
If leaking: do not use; replace the pen and contact your provider/supplier for advice.
The pen is leaking
The pen has been stored above 30C
The pen has been stored below 2C
The Mounjaro pen has been open or out of cold storage (2C-8C) for more than 30 days
The Wegovy pen has been open or out of cold storage (2C-8C) for more than 6 weeks
The manufacturers’ guidance on these pens suggest that if they are improperly stored or not used within the right timeframe from opening, then they must be discarded.
Don’t make up the missed or partial dose without first speaking to your prescriber.
I don’t think I have had a full dose of the medicine
I have forgotten a dose of the medicine
If you suspect you have been supplied a faulty or fake pen, do not use it. You should:
Report the incident to the MHRA
Report the incident to your prescriber and the pharmacy who dispensed your pen
Under no circumstances use the pen.
My pen doesn’t look legitimate