If the stool is dark and smelly, it is possible that the patient has gastrointestinal bleeding. First of all, it is recommended to clarify the routine stool examination to see if there is positive occult blood, and it is also recommended to review the routine blood test to see if there is anemia, that is, if the hemoglobin has decreased. If there is a decrease in hemoglobin and positive fecal occult blood, it indicates the presence of gastrointestinal bleeding, which requires further improvement of gastroscopy to rule out the presence of organic lesions, which requires further active treatment. Patients who have negative fecal occult blood may also have a relationship with the food they consume, such as excessive intake of meat or blood clots, which can lead to dark stools. If there are Chinese medicines, iron or bismuth supplements that are usually taken, they can all cause the stool to be black in color. If the color is black and smelly, it is necessary to consider the possibility of gastrointestinal bleeding.