My kitty developed DKA suddenly (trace ketones can become large ketones very quickly). He was 11 years old, and he was new to being a diabetic, and I was not checking for ketones at the time. He had been throwing up (projectile vomiting) and not eating and lethargic when I returned home from work. I took him to the local ER that night and stayed there while they tried to help him. In the morning, I was told that I had to take him to another hospital (as they were only open nights and weekends) that was over an hour's drive away. He was in critical condition. I just prayed the whole way there. He was in that hospital for 8 and 1/2 long days. I remember it well, the praying, the fear, and the worry, and how all I could think about was him, outside of work. He was at the University of Pennsylvania School of Veterinary Medicine, so maybe that's why it didn't cost as much as maybe another ER. It was about $4500 for his stay. Which I always considered cheap compared to what a human would have to pay for such a lengthy stay in critical care, and then ICU, and then something in between, and then in Internal Medicine, getting round the clock 24 hour care, 2 transfusions, an IV hooked up in each leg, and they said they bathed him ? daily. Anyway, he very very slowly got better and better, but would not eat the entire time he was at the hospital, so he had to come home with a feeding tube. The feeding tube was hard for me the first day. The second day, I went to get him to feed him, and he had pulled the feeding tube out. I was on the phone to my regular local vet to find out what to do and they were telling me they could re-insert it when I looked down and he was chowing away at a bowl of cat food, so no more feeding tube.
I tested for ketones from then on. He never got them again. He was diabetic of 9 years and passed away at the ripe old age of 20.