Hi,
I know diabetes can be a very frustrating disease in cats. It sometimes takes a little while to get them on the correct dose of insulin to get their blood sugars to even out. We all start with a certain standard dose based on blood sugar and weight. Very rarely do you hit the right dose on the first try. As we are all different and respond to different meds differently, so do cats. The dose then gets lowered or raised based on what the blood sugar results turn out to be. It seems like a long and trying process, but it will work. Try to be patient, you will get there.
I realize hypoglycemia is an extremely scary thing to have happen. Did he have seizures from too low blood sugar, or was he just dazed? Did you try karo syrup on his gums to increase his blood sugar? You certainly did the right thing in getting him help immediately, but sometimes a little karo on the gums will give you a little time to have him seen.
Although some cats will need to be on insulin for the rest of their lives, it is sometimes possible to get them weaned off the insulin and on the diet alone after some time. Your vet can help guide you to this if that is the right course of action. You have a ways to go, and I wouldn't expect him to be able to be off the insulin anytime soon, but it may be something to look forward to in the future.
I hope I helped, and if you have any further questions or concerns, feel free to reply and I will get back to you as soon as possible. Good luck and thanks,
Dr. CW
Cat Veterinarian
9 & 1/2 years of clinical small animal medical and surgical experience.