Determining if your cat has a serious health problem is difficult because cats tend to hide their discomfort even when they are quite ill, explains PetMD. However, behaviors such as frequent trips to the litter box or urinating outside the litter box often indicate something is physically wrong. Lower urinary tract infections frequently manifest this way. More overt symptoms, such as licking the genital area, vomiting and lethargy, sometimes occur if the infection persists.
Arthritis is another illness that frequently goes unnoticed by cat owners. If a cat does not use its litter box, hesitates when jumping or suddenly neglects its grooming, it may suffer from painful joints. Obesity, a common and frequently overlooked condition in indoor cats, contributes to this problem and puts unnecessary strain on the animal's liver and heart, according to PetMD.
If a cat doesn't appear to have a waist when viewed from above, and the owner can't feel its ribs easily, it is probably overweight, notes WebMD. A sagging abdomen is another sign that a cat is overweight.
Yet another condition that is difficult to detect in cats is hyperthyroidism, reports PetMD. Cats with this affliction have very good appetites, are extremely active and sometimes lose weight, all of which the owner may believe are signs of good health.
Other important signs that a cat may be ill include decreased appetite, weight loss and gum disease. However, changes in behavior, such as irritability, aggression, hiding, demanding attention and increased vocalization are sometimes indications of serious diseases, explains PetMD. Only a trained veterinarian can determine with certainty what, if anything, is wrong with a pet.