Symptoms of high blood sugar in dogs are as follows:

Drink water frequently. Because blood sugar levels are too high, your dog will feel thirsty and need to drink water frequently.

Increased appetite and weight loss. Although the dog's appetite increases, due to reduced insulin secretion, the body cannot fully utilize energy, so it may eat more and less and lose weight.

Frequent urination and urgent urination. A large amount of glucose enters the kidneys, and the kidneys need to filter more water to excrete the excess glucose, causing the dog to need to urinate frequently.