Fasting a diabetic dog for 24 hours is one of the most dangerous things I have ever heard. There are many different diets out there for diabetic dogs. The trick is finding the one that works with the insulin to keep your dog well maintained. My dog has been diabetic for five years. What works for my dog may not work for the next person. I personally feed Nutrisca with a topper of either Merrick canned or Grandma Lucy’s Pure Performance. I stay away from potatoes and tapioca for my dog. You might google diabetic diets for dogs and find a great article from the Whole Dog Journal. It is quite informative and gives examples of different diets that owners have successfully used to maintain their dogs. If you don’t home test, I would start ASAP.
