Black stool can be caused by several factors. One common cause is bleeding in the upper gastrointestinal (GI) tract, including the esophagus, stomach, or the beginning of the small intestine. When blood from these areas is digested as it moves through the GI tract, it turns the stool black and often tarry (melena). This kind of bleeding may come from conditions such as peptic ulcers, gastritis, esophageal tears, varices, or even cancer in the digestive tract. However, black stools can also be caused by non-serious factors like eating certain dark-colored foods (black licorice, blueberries, blood sausage), taking iron supplements, medications containing bismuth (e.g., Pepto-Bismol), or activated charcoal. These do not involve bleeding and usually resolve when these substances are stopped. If black stool is accompanied by other symptoms like stomach pain, vomiting, or continues over several days, it is important to seek medical evaluation to rule out serious conditions like internal bleeding or cancer.
