Kris,
Is it BCP PZI?
It will work, just like every insulin, differently for each cat. But generally:
Onset is about 2 hours after the shot.
Peak (nadir) between 5-7 hours after the shot
Duration 8-10 hours
Expiration - there should be a date on the vial or the box it came in, and it should be kept in the fridge.
I used PZI with my cat, Bob. His nadir was usually between +5 and +6, and the duration seemed to be 9-10 hours. I didn't test in the first couple of hours after the shot, so I don't know when the onset was.
Can you tell us what sort of BG numbers Toots has had, and if you are home testing? Also, what is his/her diet currently?
Carl