Black stools often indicate gastrointestinal bleeding. When the gastrointestinal tract bleeds iron from hemoglobin in damaged red blood cells combines with sulfide in the intestine to produce iron sulfide, giving the stool a pitchy black color. Black stools mostly indicate upper gastrointestinal bleeding or intestinal bleeding, and colon bleeding is mostly blood or dark red blood in the stool. The most common diseases in upper gastrointestinal bleeding are bleeding gastric or duodenal ulcer, bleeding acute gastric mucosal lesions, bleeding gastric cancer, and bleeding from ruptured esophagogastric fundic varices. Patients are advised to go to the hospital as soon as possible to avoid delaying the diagnosis and treatment of the disease. In addition, having eaten blood products, such as chicken blood, duck blood, pig blood, sheep blood and other blood products can cause black stools. It may also be oral medications such as those containing carbon or other drugs that also cause dark black stools. So there are many causes of dark stools, which may be gastrointestinal disorders.