Your cat may become more withdrawn or clingy, or they may start to hide. They may also lose interest in their favorite activities, such as playing or eating.
Your cat may lose weight, their fur may become dull, and their eyes may become sunken. They may also start to have difficulty grooming themselves.
Your cat may start to breathe more rapidly or with difficulty. They may also make wheezing or coughing noises.
Your cat may stop eating altogether, or they may only eat small amounts of food. They may also start to vomit or have diarrhea.
Your cat may start to urinate or defecate more frequently than usual. Their urine or feces may also be more concentrated or watery.
Your cat may start to limp or cry out in pain. They may also become more irritable or aggressive.
Your cat may become unconscious or unresponsive. This is a sign that their body is shutting down and that they are close to death.