Cats can’t always tell you when they’re feeling under the weather, so it’s up to you to watch for changes in their behavior. Given that cats are often psychotic and change their behavior faster than most people change their socks, spotting unusual behavior can be difficult, but try it anyway.
One common health symptom is when cats hide more often than usual. Another is when cats yowl or miss the litter box more than normal. Also notice if your cat changes his or her eating patterns because cats, like humans, tend to like routine for comfort.
By spotting potential health problems early, you can insure that your cat remains healthy and safe for years to come. Now you just have to worry about ignoring your own health symptoms.