A diabetic cat is very easy, our PATCHS was with us for almost 18 years.
She ate regular food and got her shot every morning. In the end she had no teeth and her caterats were so bad that I know she could not see from one eye and very little from the other, but she still rulled the house. She was never a large cat she averaged 6-7 pounds. I watched her put our Main coon in his place one day. I still miss her.