Dark green stools are associated with gastrointestinal bleeding, improper dietary intake, and iron medication. Under normal circumstances, the color of the stool should be dark yellow, once the discharge of dark green stool accompanied by abdominal distension, abdominal pain, diarrhea and other symptoms, should be alert to the occurrence of gastrointestinal bleeding caused by. In the case of gastrointestinal bleeding, not only will there be abdominal pain, but also the blood will be oxidized by the digestive juices after entering the intestine, and because the hemoglobin content of the blood is particularly high, it will form dark green after being oxidized. After a large intake of blood products and green food in the diet, the feces excreted will be mainly dark green, mainly because the iron content in blood products is too high and will be oxidized to ferrous sulfate by the intestinal digestive juices, and the green pigment in green food cannot be absorbed by the body and will be excreted along with the food residue. Some people have dark green stools because of the use of drugs, blood supplementation drugs contain a lot of iron, when the iron can not be completely absorbed by the body, it will be excreted along with food residues, so the excreted stool is dark green.