We have two (currently)-- one is now past the insulin phase, after about 3 years on it, and stable; the other is stable now, after about 7 months, BUT: The first insulin we tried, he had a massive reaction to it, and WENT MOSTLY BLIND.... it affected his optic nerves, some sort of inflammatory process, and he still has good and bad days, vision-wise, and 'good' isn't really good.... most of the time his eyes are just dilated way out and not seeing much at all. Also, it wasn't regulating his sugar or fructosamine levels worth a damn either. We switched him immediately to another type of feline insulin, the one the other cat had been using, and we got him stable, so he's very happy and healthy and weight-stable and all-- just, mostly blind. So we have two diabetic cats, one of whom is an official FDA Adverse Drug Reaction Report.

It simply takes time- as others have said, every cat is different and their metabolisms take time to adjust and readjust-- keep trying, watch the diet, monitor his sugar and fructosamine, and LOVE HIM-- it's no more fun for him than it is for you...... and I know varying recommendations from different vets can make you nuts, too, but everyone's just guessing, hoping to find the right levels and frequencies and then hoping the cat's metabolism doesn't change again......