How are things doing?
I'm on my way out the door, so I haven't had time to read the other replies.
It took awhile to determine the correct insulin dose. I have fogged out, but I think that involved initially multiple trips to the vet and one or two days staying in there so he could measure the blood sugar level 2 or 3 times that day. That determines not only the dose but if once or twice a day shots are needed. Then we were okay except things needed adjusting once more later.
I understand rare cats have trouble stabilizing on a dose, but the word there is rare.
The only time my cat got into trouble was when the vet was out of town and a new assistant kept the insulin dose high. He went into too much insulin trouble, but Karo syrup rubbed in his mouth brought him out of it. At the vet's direction, I had bottles of Karo syrup even in the car.
It was a lot easier to deal with that I had feared.
Insulin shots are not hard to give either, surprisingly, your vet can show you how.
Good news is cats are less sensitive to diabetes damage than humans, so you can err on the side of low treatment for some time if needed.
As this is coming back to me, he was on insulin for several years, then didn't need it any more.