When you look at the stool with the naked eye after defecation, the color of the stool is black, with mucus attached to the surface of the stool, and the color is shiny, also known as tarry stool. When black stool is found, it indicates the possibility of gastrointestinal bleeding, and the amount of bleeding is relatively small and the location of bleeding is relatively high, which can be in the esophagus, stomach or small intestine. The nature of the bleeding may be inflammatory, a polyp, or a tumor. After finding black stool, in addition to the pathological state, the influence of common drugs or foods should be excluded. Common foods that cause black stools include animal blood or pig liver, and common medications include bismuth preparations, iron supplements, and some herbal medicines. When a black stool is found, a fecal occult blood test should be performed. A positive occult blood test indicates gastrointestinal bleeding, while a negative occult blood test indicates interference from food or medication. Therefore, when black stool is found, you need to go to the hospital and let the doctor prescribe the necessary tests to clarify the diagnosis according to the specific situation.