Stop diarrhea in a cat by keeping it from accessing food for 12 to 24 hours and giving it only water, as suggested by HowStuffWorks. Only after this time period can the cat be given something more substantial, such as bland rice.
If a 12-to-24 hour food fast does not stop diarrhea, sometimes feeding it a bulk-forming laxative normalizes its stools and bowel movements, explains HowStuffWorks. Sometimes it is necessary to change the cat's diet, feeding it more natural and less processed foods that do not contain artificial ingredients and dyes. Diet changes can cause diarrhea, however, so first consult with a veterinarian before making any permanent adjustments.
If the diarrhea is explosive, lasts longer than a day, contains blood, or is accompanied by vomiting or fever, the owner needs to consult a professional, WebMD advises. These can be symptoms of a more serious condition, such as kidney or liver disease, cancer of the digestive tract, or inflammatory bowel disease.
Sometimes diarrhea results from allergies or food intolerance, as stated by WebMD. For instance, milk can cause diarrhea. If the cat has recently eaten any foods containing dairy, the owner needs to keep those foods away from the cat to prevent future episodes.