How do I assess whether a change in my cat's behavior means they're sick? - Countryside Veterinary Clinic

Well, certainly, if they're not eating or not drinking, if they're vomiting, having diarrhea, or if they're not urinating or not pooping, those would indicate a medical problem. If the cat is not interacting with you the way they usually do or sleeping all the time, those would be the things you would be looking for to indicate a problem.