It might sound like a page out of a spy novel, but your cat is a master of disguise. Unfortunately, this skill isn’t always in your cat’s best interest. That’s because felines are adept at hiding health issues until illnesses can escalate into serious problems.

“It’s the nature of cats,” explains Dr. Eileen R. Adamo, DVM, who runs a felines-only practice in Penfield, N.Y. “They kind of put on a good face, show they’re fine. They are masters of hiding illness and pain.”

Your cat disguises its aches and pains because showing weakness would have made its feline ancestors more vulnerable in the wild, Dr. Adamo says. Your kitty will be vulnerable, as well, if you don’t pay attention to health warning signs. It’s important to recognize when outwardly minor symptoms could indicate a more significant, underlying problem.

“You have to be super sensitive to any change,” Dr. Adamo advises. Here are warning signs Dr. Adamo and other experts say you should never ignore:

• Increased vocalization If you’re suddenly holding a pillow over your ears at night because your furry friend is yowling, your cat is actually trying to tell you something. The howling or yowling could be a sign of several health issues, say the experts. For example, a cat that howls at night could have thyroid problems, says Dr. Jessica Stern, DVM, who runs a feline veterinary practice in Columbus, Ohio. Left untreated, hyperthyroidism can affect almost every aspect of a cat’s health and even cause heart problems. If hyperthyroidism is suspected, your veterinarian will likely order blood work and a test to check thyroid-related hormone levels. Among treatment options are medications and surgical removal of the thyroid. Yowling could also be a sign of high blood pressure or even cognitive changes in an older cat, says Dr. Adamo.
  
  
• Changes in litter box behavior If your cat suddenly stops using the litter box to urinate, it could indicate a urinary tract infection or urinary tract disease, says Dr. Stern. Left untreated, some urinary problems can lead to life-threatening obstructions. If you notice that your cat is producing more urine than usual, it could signal the onset of diabetes, hyperthyroidism or chronic progressive kidney disease, says Dr. Adamo. Diabetes can be managed with early detection, and your veterinarian might prescribe oral medications or insulin injections. Progressive kidney disease is a common and serious condition affecting older cats, but treatment plans could slow down the disease’s progression.
  
  
• Bad breath If you catch an unpleasant whiff every time your cat opens its mouth, it’s time for a checkup. Bad breath isn’t the norm for cats. It can be a sign of dental disease, even if your cat is still eating regularly, says Dr. Adamo. “People tend to think, ‘If I had a sore tooth, I wouldn’t want to eat,’” she says. “Cats will find a way to eat even with a sore mouth.” Dental disease can lead to abscesses, bone loss, loose teeth and even infection that can spread to other parts of your cat’s body. Bad breath could also be a warning sign of an oral mass or kidney disease, cautions Dr. Stern. Your veterinarian will likely place your cat under general anesthesia to clean its teeth or perform needed extractions. You can help maintain your cat’s dental health by brushing its teeth with products designed for felines.
  
  
• Vomiting It’s not a pleasant task, but you need to know whether your cat is coughing up hairballs or vomiting. “People are very quick to write off vomiting in cats,” Dr. Adamo says. An occasional hairball with its distinctive tubular shape isn’t usually cause for concern. However, if your cat throws up more than once a month, it’s time to visit your veterinarian, says Dr. Adamo. Increased vomiting can be related to pancreatitis and/or inflammatory bowel disease. Acute pancreatitis may be life threatening, and inflammatory bowel disease is a chronic condition that can require dietary management and anti-inflammatory medication.
  
  
• Dinnertime pickiness Your cat suddenly turns its nose up at its favorite food. Is your friend becoming a demanding gourmand? If your cat walks up to its food dish and then walks away without eating, it could be feeling nauseous, say the experts. Nausea can have many underlying causes, such as liver disease, kidney disease and inflammatory bowel disease. Your veterinarian will evaluate the cause of the nausea and may prescribe medication to relieve the symptoms.
  
  
• Changes in grooming If your kitty isn’t grooming as thoroughly as usual, it could have an endocrine disease, such as feline diabetes or kidney disease, says Dr. Stern. Your cat’s endocrine system includes glands and organs that produce regulating hormones. Problems with the system can affect your kitty’s grooming habits. An unkempt cat might also be suffering from oral discomfort or arthritis, both of which can be eased with proper veterinary care.
  
  
• Social interaction Too often, feline owners attribute their pet’s sudden aloofness to the nature of cats, says Dr. Adamo. “If your cat is dragging itself under the bed, going off into its own area when it normally would be socializing, that’s a big clue,” she says. Your cat might be anxious, stressed or in pain. A visit to your veterinarian can help to determine the cause of your cat’s behavior.

If you notice any of these symptoms or other changes in your cat’s behavior, don’t hesitate, says Dr. Adamo. Either call your veterinarian to ask if a symptom is worth further evaluation or schedule a visit. And don’t feel like you have to diagnose the problem right then and there. “Don’t wait and don’t feel like you’ve got to figure it out,” says Dr. Adamo. “You don’t need to worry about that. We’ll sort that out. That’s what you’re paying me for.”