Welcome to our forum. You should start by reading some of the information here. If you have any questions, post them on the main health forum. There is a bunch of helpful people who have gone through almost everything a cat can have. This is just the introduction forum. Most people are on the health forum.
Have you started on testing his glucose at home? If he is on insulin, it is important to test before feeding and giving the shot. Otherwise, you risk having a kitty with hypoglycemia, a serious and sometimes fatal condition. You have a choice between a pet meter like your vet uses or a human meter. The strips for the human meter are much less expensive. Sometimes we use a lot of strips. You will find that the people here will be a life saver and some of the nicest people you could ever meet.