Old Cat Diarrhea: Causes and Treatment for Diarrhea in Senior Cats

By: Dr. Byron de la NavarreUpdated:

old cat diarrhea

Old Cat Diarrhea: Causes and Treatment for Diarrhea in Senior Cats

After practicing as a veterinarian for more than 20 years and being chief of staff at Animal House of Chicago, I have treated my fair share of old cat diarrhea. These cases have ranged from something simple, like a cat eating too many cat treats, to something more complex, like a senior cat with an overactive thyroid condition. I don’t like to see any cat suffering from diarrhea, but it can be especially difficult for senior cats (age 11 and older) to handle.

When a senior cat has diarrhea, it’s most likely a sign of another ailment, such as pancreatitis, hyperthyroidism or stress. Stress can be triggered by a recent move, new pets in the house, the loss of a pet and many other things. Think about anything that might have changed recently in your cat’s life. You and your veterinarian might have to play detective to determine the cause of your elderly cat’s diarrhea.

Knowing the cause of the diarrhea is the first step to preventing any recurrence. Overactive thyroid, food allergies, kidney failure, cancer, poisoning (from houseplants, rat poison, human medications, parasites and infectious disease, among other things), can all result in diarrhea. Obtain veterinary assistance if the cause isn’t apparent or it is an ongoing problem. A cat food with fewer allergens or treatments for a disease might reduce or eliminate the diarrhea.

Symptoms of Old Cat Diarrhea

The signs of diarrhea can be quite diverse in any age cat. Frequent, urgent pooping of loose, watery stools are the classic signs that your senior cat has diarrhea. And a cat who has a bout of watery poop and then continues to strain is not suffering from constipation; it truly is diarrhea.

The following signs of illness often accompany diarrhea:

  • Fever
  • Lethargy
  • Malaise
  • Loss of appetite
  • Dehydration

Check your indoor cat’s litter box if you suspect diarrhea. If your cat goes outside, you’ll have to observe them go, or look for their poop after. If your cat is producing loose, watery stools and it persists for more than a day, take a sample to your veterinarian.

When Is Old Cat Diarrhea an Emergency?

Senior cats, along with kittens and small-sized adult cats, are at special risk of becoming dehydrated from even a single episode of diarrhea. Use these guidelines to determine if you need to rush to your veterinarian.

If your cat seems OK after a single bout of diarrhea, it may be safe to simply monitor them. However, if you notice any lethargy, fever or change in behavior, call your veterinarian for an appointment as soon as possible.

If your cat seems fine but has recurrent episodes of diarrhea that do not seem to be resolving, call your veterinarian for a non-emergency appointment.

If your cat is passing blood in their stools or if you notice any weakness or other signs of debilitation along with the diarrhea, contact your veterinarian immediately and have your cat seen as soon as possible. Red blood in the poop usually indicates a problem with the lower intestine/colon or rectum. Black blood in the poop usually indicates a more serious problem higher up in the digestive tract.

It's important to know the signs of an emergency. Call you veterinarian immediately if your cat has diarrhea and:

  • Blood in the diarrhea or the poop is black or tarry
  • You suspect your cat may have eaten something toxic or poisonous
  • A fever, is depressed or seems dehydrated, or if your cat’s gums are pale or yellow
  • Appears to be in pain or discomfort
  • Is also vomiting

Learn more signs of a true cat emergency.

If you see no emergency signs, call your vet and ask about over-the-counter medications or options for at-home treatments for your cat. Because there are so many causes of diarrhea, the treatment will vary.

Important note: If anyone in your household also has diarrhea, take your cat to the vet and the person to the doctor right away. Some microscopic parasites (Giardia and toxoplasmosis) can cross species boundaries and can be difficult to eliminate. These parasites have the potential to become life-threatening to small children, elderly adults and those with compromised health.

At-Home Treatment for Old Cat Diarrhea

Depending on the cause of your elderly cat’s diarrhea, you may be able to help your pet with a simple change in diet or home remedy. Here are a few of the treatment options available to you and your senior cat.

Changing Food

If your senior cat has a bout of diarrhea but is acting normal and seems otherwise healthy, ask your veterinarian if you should withhold food (but not water) for 12 hours. After 12 hours of withholding food only, offer your cat a bland food that is fat-free. Some options are a fat-free prepared/canned cat food, cooked, ground turkey and canned 100 percent pumpkin. If canned pumpkin is not easily found, try fresh, cooked sweet potato.

Pets with diarrhea usually tolerate and digest pumpkin or sweet potato. Mix together equal parts turkey and pumpkin and feed it to your cat in small amounts, upping the frequency until the diarrhea resolves. If the diarrhea does not resolve in the first two to three days on a bland diet, consult your veterinarian if you haven’t already. A bland ground beef and rice diet is another option, but it will have a higher fat content, and the rice might ferment in your cat’s gut and make your cat gassy.

For some cases of diarrhea, it may be necessary to modify the diet permanently. Special foods may need to be given in order to avoid certain ingredients, add fiber to the diet and decrease the fat intake, or increase digestibility. While no single diet is ideal for every cat, some that are high in soluble and insoluble fiber, like Royal Canin Veterinary Diet Gastrointestinal Moderate Calorie Canned Cat Food or Solid Gold Let’s Stay In Salmon, Lentil & Apple Recipe Adult Grain-Free Indoor Dry Cat Food, help some cats with chronic diarrhea.

If you decide to switch your cat’s food, introduce it gradually, mixing it with the old brand in increasing amounts over a period of days to ensure an easier transition for your pet’s GI tract.

Find out more about cat food for all ages.

Natural Remedies

You can also consult your veterinarian to determine whether some natural remedies might work for your cat’s age and state of health. Slippery elm might ease diarrhea by reducing GI inflammation and providing a non-irritating source of fiber to bulk the stool and slow its transit through the GI tract. Peppermint or chamomile may help ease the cramps and other unpleasant GI symptoms that come with diarrhea. Homeopathic podophyllum is also a good remedy to keep on hand to help reduce some of the side effects associated with intermittent diarrhea. Consult your veterinarian for all dosage recommendations.

Metamucil can also be used to help resolve diarrhea. Adding half a teaspoon of Metamucil to your cat’s food with each feeding, especially if they have soft poop, often normalizes the poop.

Avoid Dairy

Avoid giving your cat dairy foods, no matter how much he may seem to like them! Almost all cats enjoy the taste of milk or yogurt, but some adult cats do not have a sufficient amount of lactase, the enzyme necessary for the digestion of dairy products. Undigested lactose moves to the large intestine, where it ferments—and can cause a cat to have gas or diarrhea.

Keep Your Cat Hydrated

A senior cat suffering diarrhea needs more water by whatever means possible. Diarrhea causes fluid loss, and the electrolytes in those fluids are essential to help control important physiologic functions.

Pedialyte is an over-the-counter electrolyte beverage designed for infants and children and can be added to your cat’s water in a ratio of anywhere from 10 to 50 percent Pedialyte to water. It comes in several different flavors, but I find the original, clear, unflavored variety to be the most accepted by cats.

To detect dehydration, gently pinch the normally loose skin at the back of the neck. The skin snaps right back down in a properly hydrated cat. If the pinched skin flattens slowly or remains tented, the cat is dehydrated.

A dehydrated cat needs immediate veterinary care. If your veterinarian determines your senior cat is dehydrated, supplemental fluids may be given either via intravenous or subcutaneous route. Drinking is no longer sufficient to make up for the dehydration because the liquids pass through the cat too rapidly to be properly absorbed.

Learn more about how to help a dehydrated cat.

Veterinary Treatment for Old Cat Diarrhea

When you first consult your veterinarian about your elderly cat’s diarrhea, they will ask you a series of questions to determine the severity of the diarrhea. When did the diarrhea start? How many bowel movements has your cat had? What does the poop look like? Is your cat uncomfortable?

If your cat’s diarrhea continues for more than a day, or if you observe lethargy, vomiting, fever, dark-colored or bloody stools, straining to defecate, decreased appetite or unexplained weight loss, it warrants a visit to the vet.

Your veterinarian will examine your senior cat for underlying illnesses, and most likely take a sample of poop to check for the presence of internal parasites, overgrowth of bacteria or other fecal abnormalities. Your vet may also conduct blood work to identify other possible causes of the diarrhea.

Other diagnostic tests that might be recommended include X-rays, ultrasound, cultures, endoscopy and biopsy. The diagnostic tests performed and treatment recommended will depend on how the long the diarrhea has been present and the severity of your cat’s condition.

When the cause of your elderly cat’s diarrhea has been determined, your vet will proceed accordingly.


Cats who spend a lot of time outdoors may be at an increased risk for internal parasites. If parasites are present, your veterinarian will prescribe the appropriate de-wormer and/or other medication needed. Not all de-wormers kill every kind of parasite, so the exact type of parasite(s) must be identified and the appropriate anti-parasitic medication(s) selected. In many cases, de-worming must be repeated one or more times over a few weeks or more. Keep things clean to remove the worm eggs from the environment.


If bacteria are causing the diarrhea, your veterinarian will prescribe the appropriate antibiotic(s). Antibiotics may also be given if the intestine has been damaged (e.g., blood in the poop may indicate an injured intestine) and there is a chance that the injury could allow bacteria from the intestine into the bloodstream, possibly causing severe disease.

A motility drug, one that slows down how quickly food moves through the GI tract, may or may not be used. It could do more harm than good if the cause of the diarrhea is from a toxin or bacterial infection. That’s why it’s important to have an accurate diagnosis before using such a drug.

Inappropriate and Toxic Foods

Outdoor cats may have an increased risk of ingestion of inappropriate food, which could lead to diarrhea. If your cat goes outside, check that your neighbors are not feeding him. Eating too much or eating food they are not used to can give a cat diarrhea. Poisonous plants are also a concern.

Treatment for cats who have eaten a toxic substance varies based on exactly what was eaten. Sometimes there is a specific remedy available that will help counteract the toxin. Other treatments may include decontamination (inducing vomiting or giving activated charcoal, for example) to prevent more toxin from being absorbed and supportive care.

Read our complete guide to poisonous plants for cats.

Inflammatory Bowel Disease

Cats who frequently have hairballs may also experience periodic bouts of diarrhea, but this may indicate another problem, like inflammatory bowel disease, that needs to be investigated.

There are two aspects to treating a cat with inflammatory bowel disease. First, you need to find a food that doesn’t contain most (ideally all) of the cat’s inflammatory triggers. Prescription novel or hydrolyzed protein diets are usually best for this. A home-cooked diet prepared from a recipe designed by a veterinary nutritionist may be another option in some cases. If a diet change doesn’t sufficiently control the disease, a veterinarian will prescribe medications to suppress the immune system. Antibiotics may also be needed to control bacterial numbers in the gut.

Remember: Over-the-counter remedies like Pepto Bismol and Kaopectate can be dangerous to cats due to salicylate toxicity. These should not be used! Always check with your veterinarian on the correct medication and dosage for the weight and age of your cat.

Not sure whether to see a vet? Use PetMD's Symptom Checker. Answer a few questions about your pet's symptoms, and the vet-created online tool will give you the most likely causes and next steps.
Although it happens, cats are not prone to diarrhea, so it’s important to pay attention when it does occur. Just remember: Your cat cannot control the diarrhea. So please do not scold your cat for the accidents. They cannot help it and adding stress may only make their diarrhea worse.
Dr. Jennifer Coates, DVM, contributed to this story.


By: Dr. Byron de la NavarreUpdated: