Reviewed for accuracy on August 17, 2018 by Jennifer Coates, DVM
Cats are naturally conditioned to mask when they’re not feeling well, so it can be difficult to detect signs of cat illness right away. However, when a cat is sick, there can be some noticeable changes in their behavior.
In fact, cat behavior often changes long before you start seeing any physical symptoms—so be on the lookout for fluctuations in the way your cat behaves, and see your veterinarian if you notice something unusual.
Here are 10 weird cat behaviors that could be signs your cat is sick.
A lot of people would worry if their cat stops eating, but an increase in appetite could also be a sign of a sick cat.
“Sudden appetite changes can indicate your cat has underlying health problems and warrants a visit to the veterinarian,” says Dr. Rachel Barrack, DVM, CVA, CVCH of Animal Acupuncture in NYC. “Increased appetite can be due to endocrine disorders, such as diabetes or even hyperthyroidism, or nutrient malabsorption issues such as intestinal cancer or inflammatory bowel disease.”
Increased water intake can definitely be a sign of a sick cat, according to Dr. Kelly Ryan, DVM, director of veterinary services at the Humane Society of Missouri’s Animal Medical Center of Mid-America. “And while cats need plenty of fresh water, drinking too much can indicate kidney disease in cats, diabetes or thyroid problems,” Dr. Ryan says.
Cats can stop grooming for a multitude of reasons, and this can be a sign that your cat is sick and should see a veterinarian, according to Dr. Barrack. “For example, overweight cats may not be physically able to groom,” says Dr. Barrack. “In addition, obesity can cause many health problems, including cancer, diabetes and decreased life expectancy and quality of life.”
Decreased grooming can also be connected to pain from dental disease, injury or arthritis, according to Dr. Barrack. “In senior cats, decreased grooming may be attributable to senility,” she adds.
Meowing is an important way that cats communicate with humans, so if they are sick they may be more vocal, and the sound of their meow might be different, explains Dr. Ryan.
One thing to keep in mind is that some cats are more vocal than others, so just because your cat is talking, it doesn’t mean he’s sick. “However, if you normally have a quiet kitty who’s now meowing a lot, it might be time for a vet visit,” says Dr. Ryan.
The opposite is also true. Take notice if your vocal cat becomes unexpectedly quiet. “Always consider your cat’s normal behavior, and if there are any changes, it is best to call the veterinarian,” says Dr. Ryan.
Eighty-five percent of cats have periodontal disease by the time they are 3 years old, and bad breath is one sign, according to Dr. Ryan. “Talk to your veterinarian at each wellness visit about dental cleanings and what you can do at home to prevent dental disease; not only does dental disease cause bad breath, but it can lead to more serious issues like kidney, liver and heart problems.”
While dental disease is the most common cause of bad breath in cats, there could be other reasons for bad breath. “A cat with diabetes may have a sweet-smelling breath along with increased thirst and urination,” Dr. Ryan says. “A cat with kidney disease, on the other hand, can have breath that smells like ammonia because the kidneys aren’t able to filter waste products adequately.”
When your kitty stops using the cat litter box, the underlying reason can be behavioral or medical, according to Dr. Barrack. “Behavioral reasons are usually attributable to changes in the household causing stress—a move, a new roommate (furry or human), new cat litter or less time with the owner,” Dr. Barrack explains.
“Medical issues can also cause your cat to stop using the box and may include arthritis, cancer, feline interstitial cystitis, kidney stones or urinary tract infections. Bring your cat to your veterinarian to determine if there is a medical cause of the inappropriate elimination,” says Dr. Barrack.
Pupil size changes noticeably in cats depending on the amount of light they’re exposed to, but if the changes happen at random times, or if they persist, it could be a sign of an underlying medical condition.
“Dilated pupils, constricted pupils (when the pupils look very small) or one pupil that is dilated and the other is constricted can all be a sign of illness,” says Dr. Ryan. “Because these changes can happen normally throughout the day, it’s important to consult your veterinarian if you notice a change lasting over a long period of time.”
Keep on the lookout for other indications of cat illness that are connected to the eyes, including discharge, droopy eyes or the third eyelid covering part of the eye, as well as more generalized symptoms like lethargy or a poor appetite. These can all be signs of a sick kitty.
If your sweet cat suddenly seems unusually irritable, it could be a sign your cat is sick.
“Increasing irritability can be an indication of pain and/or senility,” Dr. Barrack says. For example, cats with joint or back pain might react aggressively if you touch the area that hurts, and things like hyperthyroidism can cause your cat to be hyperactive, reacting in what sometimes seems to be a hostile manner.
A lack of interest in playing can be an indication of a sick cat, especially if you have a usually playful kitty who now seems lethargic or uninterested in playing for no apparent reason.
“You will also want to consider the circumstances,” says Dr. Ryan. “If your cat has been playing a lot or if there is a change that could cause stress, like visitors to the house or the addition of a new baby, he might not feel like playing.”
There are many theories on why cats hide when they are sick. “Some experts believe that in the wild, a cat would instinctively hide in order to stay safe, as being ill made them weak and susceptible to predators,” says Dr. Ryan.
“Others believe that cats hide when they aren’t feeling well because they simply want to be left alone to sleep and recover,” continues Dr. Ryan.
According to Dr. Ryan, hiding can be connected to any type of cat illness and it could also be a sign of injury, stress, anxiety or fear.
All cats need to take a break at times, but if your cat starts to disappear on a regular basis for long periods of time—and especially if there are also changes in eating and drinking habits and other behaviors—it is time to talk to a vet.