Welcome
What insulin and dose?
Good insulin are the human Lantus and Levemir and the pet insulins ProZinc and BCP PZI. For those two human insulin it is best to get the 5 pack of 3 ml disposable pens via a 10 ml vial. Although per ml the vial is less expensive most cats will not use up a 10 ml vial before the insulin goes bad/becomes ineffective. The human insulin N/NPH is sometimes prescribed but only lasts 8-10 hours. Same for the pet insulin Vetsulin/Caninisulin.
Most of us here test or cats blood glucose at home using a human meter. We test before each shot and periodically between shots. We record our reading and other info in a spreadsheet. See:
http://www.felinediabetes.com/FDMB/...te-a-ss-and-link-it-in-your-signature.130337/
What are you feeding? A low-carb canned is best. No reason for a prescription food. Here is a list of commercial low-carb canned
http://www.felinediabetes.com/FDMB/threads/shortcut-shopping-list-all-8-or-less-updated.117688/
If you post some BG before shot and between shots we can better help you.
My Patches II get Lantus at such BG. This evening She got 1.2 units with preshot of 66. That is based one experience of how low she will drop between shots. I have reduced the does and her BG get up into the high 100's and 200's.
I use a human meter which tends to read higher that BG determined by lab results and pet BG meters.