Signs of diabetes in a cat include excessive thirst, change in appetite and weight loss. Other symptoms that may indicate a cat has diabetes are decreased activity, depression and vomiting.
If a cat has diabetes, it may have less energy even if it is eating enough, because a diabetic cat can't use the calories it is consuming. Some cats may lose muscle mass when diabetic, which can cause weakness. Cats with diabetes may also become lethargic, stop grooming themselves and lose interest in the environment around them. Cats with prolonged diabetes may have dull hair coats and develop liver disease.