My first cat was diagnosed as diabetic at 9 years old. He lived to 17. We tested him daily - which he didn’t mind at all - and usually ended up giving him one shot of insulin per day.
He was the same old cat the entire time. I’m really glad we learned how to take care of him because now I’m not worried about having another diabetic cat. It’s just another thing to check on. Cats are just so accommodating when they know you’re taking care of them.