Black stool can be caused by a variety of factors. Common harmless causes include eating certain dark-colored foods (like black licorice, blueberries, or beets) or taking iron supplements or medications such as Pepto-Bismol. These typically do not change the smell of the stool. However, black, tarry stool can also indicate bleeding in the upper gastrointestinal tract (esophagus, stomach, or small intestine). This bleeding causes the blood to be digested and turn black, often resulting in foul-smelling, sticky stool. Serious medical conditions that can cause this include stomach ulcers, gastritis, esophageal varices, or cancers. If black stool is persistent or accompanied by symptoms like stomach pain, vomiting, or fatigue, medical attention is important to determine the cause. In summary, black stool may be due to diet or supplements, but if there is any risk of gastrointestinal bleeding, it requires prompt evaluation by a healthcare provider to rule out serious conditions.
