Update March 15th 2023
Believe it or not, Buster is still with us and doing great! He celebrates his 18th birthday on March 25th. I had no idea this video would get so many views, nor that it would help so many other families. I have LOVED reading your comments over the years. Thank you all so very much.
Buster's diabetes is transient. We control it very well with diet and swift treatment during the times he does start to slip back into hyperglycemia. I credit four things with his recovery and his long, healthy life: Fussie Cat canned cat food (34 cans/day), Orijen Original Cat dry food (1/4 cup per day, if that), Lantus insulin, and the Freestyle Libre system. The Freestyle has been useful in recent years because it allows me to check Buster's glucose without overly stressing out the old man. It's so easy, even my kids can scan him! The Fussie Cat wet food was also essential without it, I don't think I'd be sitting here typing this update. We first gave FC a try back in 2013 and haven't looked back.
I do advise caution* to anyone wishing to switch over to FC. Please make sure you have some sort of continuous glucose monitoring system like the Freestyle Libre in place for the 23 weeks after you switch food. Buster's sugar plummeted the first week I switched because his pancreas was suddenly functioning better but I hadn't adjusted his insulin dose, and he wasn't getting much sugar in the new food**. Having a CGM will help you tweak the insulin dose easily as your kitty adjusts. Once your kitty stabilizes and you have a better understanding of how their blood sugar trends, you can probably discontinue using the sensors if you're comfortable with it. They do get expensive! We only use maybe 23 a year now, when it seems like Buster might be trending towards diabetes again (usually after he gets into the dog food, ugh).
Thank you again, everyone, for your comments and kind words for the last decade+. I wish you all the best of luck with your sugar kitties!

*I am not a vet, and my advice is based only on our personal experience with Buster and a handful of other cats we've known through friends and family. I am not promoting any sort of cure. I'm only highlighting what worked for us, what risks we encountered, and how we managed them just in case anyone else was thinking of trying these things.
**Fussie Cat has fructooligosaccharides, which contrary to popular belief are NOT a digestible sugar and therefore do not increase blood glucose levels. FOS are a sort of prebiotic.

My cat is diabetic and he went into a diabetic shock a few months ago. The first and most visible symptom of feline diabetic shock is seizures. The problem back then was that if you've never seen a cat having a seizure, it can be hard to recognize. So when he went into shock again earlier today I decided to film one of the seizures and post it here. Maybe it will help someone. Diabetic shock is very deadly to cats.

Btw He's fine now. The vet said he's starting to ease out of his diabetes!