A coworker one day told me she had a farm cat who was part Maine Coon and polydactal (an extra toe) who had had an accident resulting in the loss of one leg and an eye and now the barn cats would not let him return to the barn, they picked on him. She was looking for a home in a house for him and I took this wonderful cat who did well for about a year and then started loosing weight.
He was not over weight or older and so the vet said he did not think it was a "sugar" problem but we would check that and other things. He was diabetic.
I was overwhelmed. I did NOT want to give insulin to my pet but it was that or loose him. His management was hard and he had a couple insulin reactions resulting in unconsciousness and having to give him Karo syrup. He also seizured after one of them. But we are now under control and for the last 3 years no insulin reactions, he is gaining the weight he lost and when I hold the syringe and call him he comes. He sticks to his diet only because he can not open the food containers. Dact is an example that a cat can live with this and flurish. He gets two shots a day and I have a couple friends who help when I am not home as he has not learned to give his own.
If you find yourself with a diabetic pet, give him a chance. Dact is a great friend and lives a quality life.