Although cats outnumber dogs in the U-S by about 15 million, most don’t see the veterinarian as often as their canine counterparts. One reason is that it can be tough to tell if your feline friend is sick.

Signs of illness can include a change in behavior, an unkempt appearance and bad breath. Decreased eating or drinking or altered litter box habits are also warnings that something is up. Even an increase in eating or drinking can signal a problem with your cat. Some symptoms can cause problems of their own, and a cat that hasn’t been eating or drinking for 24 hours needs to be seen by a veterinarian immediately.

If your cat seems “off,” trust your instincts. Even a change in your pal’s “meow” may be telling you something. Regular wellness exams will also help your vet detect health problems before they become serious.