Cats With Weight Loss & Dark & Soft Stool

Cats can suffer several intestinal and systemic conditions that can cause weight loss and stool problems.

Cats can suffer several intestinal and systemic conditions that can cause weight loss and stool problems.

Cats whose stool is dark and soft should see a vet right away. The same is true of cats who are losing weight. Combined, these conditions could be the result of serious issues such as colitis, parasites, inflammatory bowel disease and other painful or life-threatening illnesses.


Colitis is a general term referring to inflammation of the colon. Several types exist; each has a different cause, but all have similar symptoms. Changes in stool are common with colitis, including loose stool, diarrhea or stool with old or new blood. In chronic cases, a cat may experience appetite loss and may not be able to absorb nutrients; both can lead to weight loss. Although a cat may not appear to be in pain, colitis is a very painful condition.


Cats can get several types of parasites, including hookworms, roundworms, tapeworms and others. These parasites, aka worms, infest the intestines. Parasite infestations can cause symptoms including diarrhea, bloody stool and weight loss, among other problems. Outdoor cats, those deprived of regular vet care, and unvaccinated cats are most at risk for parasites. Worms can pass to other pets or people if eggs are ingested. Proper vet care is needed to address the infestation.

Inflammatory Bowel Disease

Like colitis, inflammatory bowel disease is a general term for a condition with many roots. Unlike colitis, which affects the colon, IBD can cause inflammation in any part of the gastrointestinal tract. Over time, this causes intestinal damage and reduces the body's ability to absorb nutrients. This can result in weight loss and loose, watery or bloody stools. In early stages, symptoms may be mild, meaning some cats may suffer IBD for lengths of time before obvious symptoms appear.

Treatment Options

For colitis and IBD, some of the treatment options are similar. They include feeding highly digestible foods, and foods unlikely to cause allergic or adverse reactions. Drugs or anti-inflammatory supplements like omega-3s are options. In the case of parasites, a vet can administer an oral worming agent. Other diseases like cancer can cause weight loss and dark, loose stools. Testing a cat's blood, urine and feces, conducting X-rays or ultrasounds, or biopsying tissue can help screen for causes.

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About the Author

Sarah Whitman's work has been featured in newspapers, magazines, websites and informational booklets. She is currently pursuing a master's degree in nutrition, and her projects feature nutrition and cooking, whole foods, supplements and organics. She also specializes in companion animal health, encouraging the use of whole foods, supplements and other holistic approaches to pet care.

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