Low platelet black stool, consider with thrombocytopenia caused by upper gastrointestinal bleeding related. 1. Leukemia, aplastic anemia, use of chemotherapy drugs, infections and vitamin B12, folic acid deficiency and other factors can lead to thrombocytopenia, platelet drop when the coagulation function is abnormal, easy to cause upper gastrointestinal bleeding. 2. When upper gastrointestinal bleeding occurs, the blood stays in the intestine for a long time, and the digestive juices in the intestine will digest and decompose the blood, in which the trivalent iron ions of hemoglobin will be reduced to divalent iron ions, and the color of divalent iron ions is black, so the discharged stools will be black. If you have low platelets and black stools, it is recommended that you go to the hospital to complete the relevant examinations to clarify the cause of thrombocytopenia, and under the guidance of the doctor to carry out targeted treatment.