Recent Diagnosis of Diabetes

Hey everyone,

TLDR: cat newly diagnosed with diabetes - tips for a 13y/o cat who was outdoors his entire adult life?

3 and a half years ago I found my best friend outside on my porch. He came up to my door, an old mangled black cat missing teeth and losing hair with scars across his face. He looks like he'd kill you in your sleep but became the sweetest boy ever. He was completely feral at first, only coming to eat the food I put out for my other outdoor cats (I live next to a farm and already have 4 indoor cats). Long story short, he got severely injured and lost a chunk of his face/cheek by what looked like another wild animal or some sort of trap? I had to take him to the Emergency vet and they had to put him under and give strong pain meds, so he had to stay inside to recover for a week. During that time he became warmed up to me and my other cats slowly but surely. I found out he was older (at the time i was told he was 10-ish) and I joke that he wanted to just retire after his accident because he never had any interest to go back outside. Hes been indoors for 3 years now and I love him to death. Hes so sweet to my other cats and very active and seemed healthy. However I noticed access drinking and peeing about 3 months ago, and I wasn't too concerned but recently got a bonus from work so I decided to take him to the vet for a full check up since he's never been to the vet besides the life saving care for his wounds after the accident. I was informed today he has diabetes (Blood glucose level is almost 500).

I understand the insulin injections 2x a day and I'm willing to do that for him. I just wanted to hear other people's experiences of having a cat with diabetes as this is my first one. Also if you made any adjustments to the type of food you gave them? Thank you all fellow cat lovers!!