How to Tell When a Cat Is Sick

Jennifer Grota, DVM
By Jennifer Grota, DVM on Apr. 5, 2022
Healthy cat

Cats can be excellent hunters and predators, but not everyone realizes cats can also be considered prey by some larger animals. To protect themselves, cats have developed the ability to hide injury or illness exceedingly well. They do it so well that you may never know anything is wrong until they are in a lot of pain.

If you know what sign to look for, however, you might be able to know earlier when something is wrong.

Symptoms of a Sick Cat

Pet parents will usually notice that their cat is “acting weird,” which could refer to a lot of different type of changes in behavior or habits. Here are some of the ways your cat might be telling you they’re not feeling so well.

Suddenly Eating More, Eating Less, or Not Eating

One of the first signs you might see in a sick cat is a change in appetite.

  • An increase in appetite can be caused by intestinal parasites, hyperthyroidism, diabetes, or a gastrointestinal disease that causes poor nutrient absorption.

  • Decreased appetite may be due to nausea, fever, food aversion, gastrointestinal disease, or pain in the mouth (due to dental disease, a mass, a foreign body, or trauma).

Drinking More

There are many potential causes of increased thirst in cats, including:

  • Diabetes

  • Kidney disease

  • Hyperthyroidism

  • Increased calcium

  • Less common endocrine diseases such as acromegaly or hyperadrenocorticism

  • Certain urinary prescription diets designed to increase thirst to promote frequent emptying of the bladder

Meowing or Vocalizing More

Some cats meow more than others, and this also varies by breed. However, if you notice increased meowing or a change in how your cat meows, they may be trying to communicate physical or emotional distress.

Cats may meow more when they are hungry or in pain. As cats age, some develop cognitive dysfunction, or senility, which can also change the frequency of meowing.

Suddenly Not Using the Litter Box

Seek veterinary care immediately if your cat is suddenly unable to urinate (especially male cats). They may have an obstruction in their lower urinary tract, usually in the urethra, and this is a medical emergency.

Cats may also stop using the litter box and start urinating or defecating elsewhere if they associate pain with the litter box. This can happen with a bladder infection, gastrointestinal, disease-causing diarrhea or constipation, or arthritis or other joint pain that makes it difficult to get in or out of the litter box.

Another potential reason cats avoid the litter box in multi-cat households is because one cat is guarding it and blocking the other cat from using it.

Vomiting or Diarrhea

Potential causes of vomiting and diarrhea in cats include:

Not Grooming or Overgrooming

While it may seem counterintuitive, pain can cause either an increase or a decrease in grooming behavior in cats.

For example, a cat with a painful bladder condition may overgroom their belly to the point of baldness. Some cats will also overgroom as a self-soothing behavior when they are anxious.

However, pain in a joint or multiple joints may cause a cat to avoid grooming that area altogether, so you may notice clumped or matted hair.

Cats that are obese also have difficulty grooming their hind legs and spine near the tail area, so you may see matting of the haircoat in these cats. If your cat has pain in their mouth, they may also not be able to groom comfortably.

Bad Breath

Bad breath is usually caused by dental disease (e.g., tartar, gingivitis, stomatitis, an abscessed tooth, or a mass or tumor in the mouth), but it can also be a sign of internal illnesses such as kidney disease or diabetes.

Change in Mood/Suddenly Cranky

A sudden change in your cat’s mood, like suddenly becoming cranky, may be caused by a few underlying conditions:

Call your vet if you notice a change in your cat’s mood.

Change in Pupil Size

Cat pupils should be equal in size and should react to light much the same way that human pupils do. In other words, the pupils should get smaller in bright light and larger in dim light or darkness.

Unequal pupil size, or anisocoria, is not normal in cats and may be a sign of:

  • A problem with one of the cranial nerves or the brain

  • Cancer

  • Injury to the cornea

  • Retinal disease

  • Inflammation in the eye

  • Glaucoma

Persistently larger or dilated pupils (mydriasis) may be caused by hypertension, retinal disease, or a tumor affecting a cranial nerve or the brain.

Persistently small pupils (miosis) may be caused by disease in the brain or Horner’s syndrome.

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Lethargic or Unusually Hyper (Change in Energy Level)

While a change in energy level may seem like a very vague sign of illness, it can be a sign of certain health conditions.

For instance, hyperthyroid cats are often very active, while cats that seem lethargic may be suffering from arthritis or many other illnesses. A change in energy level may seem to happen all of a sudden, or it may become gradually more noticeable over time.


Cats that hide are definitely trying to communicate something to their family. Your cat may hide because they’re scared, but cats will also hide if they are stressed, in pain, or avoiding a feline or human family member that intimidates them. Some pregnant cats will also seek out a private, quiet place to deliver their kittens.

Weight Loss

A stable, healthy weight is a good indicator of overall health, while any significant change in weight can be a sign of an underlying health issue.

Weight loss can be seen in many conditions, including:

  • Poor nutrition

  • Intestinal parasites

  • Diabetes

  • Hyperthyroidism

  • Kidney disease

  • Dental disease

  • Inflammatory bowel disease

  • Irritable bowel syndrome

  • Malabsorption

  • Pancreatic disease

  • Cancer

  • Decreased appetite caused by nausea

Older cats may also lose muscle mass and look thinner overall.

Weight Gain

Weight gain is most commonly caused by overfeeding, but it may also be noted with endocrine diseases like hyperadrenocorticism or acromegaly, or with some cancerous tumors. Diseases like feline infectious peritonitis (FIP) may cause fluid to accumulate in a cat’s abdomen, causing the appearance of a large belly or being overweight.

Breathing Problems (Wheezing, Panting, Coughing)

Unlike dogs, cats do not normally pant. While cats might pant briefly after very strenuous exercise, they may also pant if they are stressed, have serious heart or lung disease, or if they are overheated.

Wheezing in cats is typically caused by asthma. Coughing may indicate a respiratory infection, bronchitis, heartworm disease, asthma, or cancer.

Eye or Ear Discharge

There should normally be little to no discharge from your cat’s eyes or ears.

  • Eye discharge may be the result of an irritant, corneal injury, bacterial or viral infection, or eyelid disease.

  • Ear discharge is most commonly caused by a bacterial or fungal infection or ear mites.

Hair Loss

If your cat is anxious or has pain in a certain area, they may overgroom to the point where they cause bald spots. Hair loss could also be caused by a bacterial infection, fungal infection (like ringworm), allergies, or parasites such as fleas.

Limping/Having Trouble Jumping Up

Changes in your cat’s gait or movement can be a good indicator that your cat is in pain. Cats will often adapt how they move when one or more of their joints is uncomfortable. 

Normal aging can result in painful arthritis that can make your cat limp. The limp or change in gait may be subtle—pay attention to how your cat jumps up or down from surfaces and how they go up and down a flight of stairs.

Extreme causes of a changed gait would be a broken bone or injury to a muscle, ligament, or tendon due to trauma.

Any changes, whether subtle or drastic, should be investigated by your vet.


Seizures can range from small facial spasms to full-body convulsions (a grand mal seizure). Causes of seizures in cats include epilepsy, a disease or tumor affecting the brain, or toxins.

Is My Cat Sick Enough to Go to the Veterinarian?

Knowing what is normal for your cat is the first step to recognizing when something is not quite right.

Not being able to pee, vomiting that won’t stop, being unresponsive, seizures, and labored breathing are all emergencies, and you should seek veterinary care immediately.

If you notice any other change in your cat’s usual behavior or any of the signs discussed, call your veterinarian to schedule an appointment. They can give you guidance as to how soon to be seen based on how severe the change is and how long it’s lasted. 

Here are a few simple things you can check at home:

  • Has your cat’s urine changed color?

  • Is your cat urinating more or less than usual?

  • Is your cat’s stool a normal color (not dark or bright red from blood)?

  • Is your cat’s stool firm?

  • Do your cat’s eyes look sunken?

  • Does your cat have tacky or sticky gums?

  • Does your cat’s skin fall back down quickly after being gently lifted?

Cats can be experts at hiding signs of illness, but if you know what is normal for your cat, you can recognize changes early on so you can take action sooner to help your feline family member.

Featured Image: Agency

Jennifer Grota, DVM


Jennifer Grota, DVM


Dr. Grota decided at an early age that she wanted to be a veterinarian. A native of Indiana, she grew up in a home where animals were...

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