Causes of Diarrhea in Dogs and Cats

Causes of Diarrhea in Dogs and Cats
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Diarrhea is the tell tale sign that your pet is not feeling their best. Learn about the causes and what they might mean here.

Diarrhea is not a disease -- it’s simply a sign that something is awry with your pet. In many cases, the cause is relatively minor; many times the diarrhea will stop without any action on your part or with relatively low-level treatment methods. Diarrhea can also be more serious and can be a symptom of diseases, parasites, or infections. Learn some of the most likely reasons your cat or dog is experiencing diarrhea.

Rapid Transit

During the ordinary process of digestion, the food a pet eats travels through the small intestine and majority of the food and water is absorbed. The remainder of the unabsorbed food and liquid continues to the colon, which processes it, allowing your cat or dog to have a normal bowel movement. When diarrhea occurs, the food travels too rapidly through the intestines, resulting in an excessively watery stool.

Diet-related issues, which can lead to this rapid transfer, are often the most likely cause of your pet’s diarrhea. For instance, dogs or outdoor cats can easily ingest something that disagrees with their stomach, like spoiled food, grass, plants, non-edible items like plastic and paper, or rotted garbage. As well, pets can have a food intolerance to something within their daily food. Even though cats crave a sip of your milk or a slurp of your ice cream, keep in mind that dairy does not agree with all cats -- like humans, some cats can lack the enzyme to digest dairy. Another dietary concern that can lead to diarrhea is an abrupt shift in food; always shift food brands and varieties gradually to ease the transition for your pet. 


Another very common reason for your pet to have diarrhea is intestinal parasites. For dogs and outdoor cats, these are particularly easy to encounter in water, fecal matter, or other animals. The likely culprits are: giardia, roundworms, hookworms, whipworms, and threadworms.

Other Common Causes

  • Stress and Environmental Factors: Changing homes, feeling anxious, stressed, or even extreme happiness can all have an impact on a pet’s stomach and gastrointestinal system.
  • Bacterial or viral infections: Bacteria, including salmonella, can cause diarrhea as cats and dogs work to purge toxic elements from their system.
  • Drugs or toxins: Antibiotics, NSAID painkillers, and dewormers and other medications can have diarrhea as a side effect.
  • Diseases: From cancer to colitis, many diseases have diarrhea as a symptom. Some diseases that are known to have diarrhea as a potential symptom include bowel disease, kidney or liver disease, and hypothyroidism.

Associated with Serious Diseases & Conditions

Diarrhea isn’t a disease, but it can be a symptom that your pet has a serious disease or condition, such as cancer, intestinal diseases, and disease of the disease and kidney. If your cat or dog has a long-lasting bout of diarrhea, or displays risk symptoms, don’t hesitate to visit the vet.

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.

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