Good resource:
Feline Diabetes —Diabetes in Cats — Treatment and Diabetic Cat Info — FDMB
Check out the part on home testing. My 15yo tortishell (Tori) has been diabetic for 6 years now. I test her periodically on an ear using a mini penlight to transilluminate the vessels along the edge of her ear. I do this immediately after putting her dish down. (Some cats won't allow this) She has done very well but does require twice daily insulin. Some cats can be controlled on once daily insulin. Talk with the vet on free feeding, that's probably going to change to get better control. Tori gets a pre-measured amount for each meal when she boards at the vet in little snack baggies (she is there now as I'm out of town for work). I feed
my other two cats in a separate room and shut the door for a while. Food is always better out of the other guys dish. Only hiccup recently was change in insulin brand as the one she was on originally is NLA. We had our first hypoglycemic episode (55) and I put pinches of brown sugar in her mouth until she was oriented enough to eat moistened dry food. Vet tech later suggested using frosting as it sticks together better and is cheap. If you are squeamish and hesitate the cat will sense this and will take control from you on injections and testing. Oh, an inexpensive glucosemeter form Walmart or Walgreens, etc will work fine for testing. I've done 3/day tests when first starting over weekends and just recently with the insulin change and much cheaper to do yourself.