This put my 10 year old yellow tabby into remission and he lived another 9 years. It was intense for several months but worth it, he was the love of my life. I got a simple insulin test kit at the drug store and he would let me prick his back foot pad after warming it up by pressing a cup of hot tap water against it, 3x a day. It turned into a snuggle session for him so, yeah, he was into it. I would alter the dose of insulin based on his last few blood values, gradually weaning him off Good luck! The raw diet was a huge factor.

https://hare-today.com/feline-nutrition/health/feline-diabetes-the-influence-of-diet

http://www.diabeticcatinternational.com/site/fd-treatment/feline-diabetes-treatment/

https://hare-today.com/raw_food_for_cats