pre filling syringes

Hiya, I am going away for the night at the weekend and leaving my mum cat sitting. I've previously showed her how to do his injections but still I have worries. The main worry is giving too much. I was wondering if I can pre fill the syringes to be prepared. I am delaying my leaving so I can watch her give him his morning jab. Then its just the evening and following morning she;ll have to give. Is it ok to do this or you think safer to trust the right amount is given?
Vet said hes never tried it and to put one in fridge and see if the insulin separates which he thinks it will, so it will need a roll so thought I'd ask you guys as im sure you have experience on the matter.

On another note we are switching over to pzi next week. Ive delayed that too as no way I want to start him on something new while I'm away.

 

As far as I know, you can prefill Caninsulin into syringes. Store the syringes with the caps on, needle side up in a cup. That way, the insulin won't clog the needle. It will likely separate in the syringe and need to be rolled.