Feline Diabetes: Ketones & blood glucose levels

Edited from a post by Hilary & Zug (GA)

Ketones are a serious side effect of diabetes. Caregivers must test their cat's urine for ketones daily when blood glucose (BG) levels are high (over 300) and a couple of times a week as long as exogeneous insulin is being given. The explanation describes 3 conditions in which high blood glucose levels can lead to ketones and 1 condition in which high blood glucose levels rarely leads to ketones.

1. Insufficient insulin. Insulin allows glucose (energy) to enter cells. Without insulin, cells starve because they don't get glucose. Insulin's like a door key -- if the key's missing, you can't open the door, and all the glucose stays on the wrong side. If the cells don't get enough glucose, they try and compensate by breaking down lipids (fat) for energy, and that causes ketones.

2. Infections. The immune response to the infection can impair insulin usage. So it's like the doors are partly barricaded, and not enough glucose can get in to feed the cells. That's why things like UTIs or bad teeth can cause ketones, even at relatively innocuous numbers.

3. Insufficient food intake. This one often seems counterintuitive, and even grasping the physiology, it took me a little while to bend my brain around this. Because even at high numbers, a cat needs a fresh infusion of nutrition-wrapped glucose for the insulin to let into the cells. kind of like the cells are watching a stale buffet get staler, and waiting for the good fresh stuff to come out of the kitchen. when it doesn't, they start looking at ways to get more/better "food", and that can mean breaking down fats and causing ketones.

4. Too much glucose. Rebound is the bodies response to an insulin dosage that is too high over time (a positive feedback loop). In rebound, glucose still enters the cells at a good rate, but MORE glucose is being dumped into the bloodstream (well, technically, more glucose is being produced via glycosis, but...). So the cells aren't starving, and they don't "feel the need" to break down fats into metabolic products they can use. Plenty of food's coming in the door, there's just a lot more out there. So the physiological mechanism that creates the high BG levels is a very different underlying physiology that won't lead to ketosis. If your cat has high BG levels and you suspect it is due to rebound, you have a little more leeway to experiment without the threat of ketones hanging over your head.

So, to put it in really simple terms there are 3 ways to get ketones:

1. High numbers (not enough insulin/ineffective insulin) --> possible ketones.
   
2. Inappetance/insufficient food intake --> possible ketones
   
3. Infections --> possible ketones

(Note that the latter 2 issues make it possible for ketones to appear at relatively "low" BGs e.g., under 300mg/dl)

When you start combining these issues, you increase the probability of developing ketones, ketosis, and potentially fatal ketoacidosis.

Thanks to Hilary & Zug(GA)