Sudden fever in cats

The most accurate way to tell when your cat has a fever is to anally measure your cat’s body temperature. Above 39.5, the cat is considered to have a fever. Cats with a fever are generally advised to go to the hospital first to reduce the fever and then check what the cat’s fever is due to, as there are indeed many causes of fever in cats. If your cat is found to be unhinged at home, then a temperature measurement needs to be taken.