Stool Color Changes (cont.)

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Black tarry stools

Black stools are a worrisome symptom because it may be due to bleeding into the gastrointestinal tract, most often the esophagus, stomach or duodenum. Red blood cells are broken down by digestive enzymes and turn the stool black. These stools tend to be tarry and foul smelling. This can be a medical emergency; black tarry stools should not be ignored.

Blood from nosebleeds or from dental procedure and injuries can be swallowed and may be the cause of black stool.

Certain foods and medications can turn stool black, including iron, bismuth (Pepto Bismol, loperamide [Kaopectate]), beets, and licorice. While the stools may be black, they also tend to be gritty and not tarry. Pregnant women may have black stools due to prenatal vitamins, which contain iron.

Bright red stools

The most common cause of bright red stool is bleeding from hemorrhoids, but other bleeding causes are much more significant. For that reason, blood in the stool should never be ignored. Other causes include infection, inflammatory bowel disease (Crohn's disease, ulcerative colitis), diverticular bleeding, tumors, and arteriovenous malformations (AVM). Brisk bleeding from the upper GI tract may cause stools to be red instead of black because there has not been enough time for the red blood cells to be digested. Red food coloring and beets can also give a reddish hue to the stool.

Light-colored white or clay-colored stools

White or clay colored stool are often seen with liver or biliary tract diseases. Lack of bile which gives stool its brown color leaves it appearing pale.

Medically Reviewed by a Doctor on 6/18/2015

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