Black stool in the morning may be caused by dietary factors, medication factors, ulcerative diseases, tumors, blood diseases and other reasons. 1. Dietary factors: for example, eating pig liver, pig’s blood, chocolate, spinach, seaweed can lead to black stools. 2. Drug factors: for example, taking iron, bismuth potassium citrate and so on may appear black stools. 3. Ulcerative diseases: for example, gastric ulcer, duodenal ulcer, stress ulcer, esophageal ulcer and other diseases may cause upper gastrointestinal bleeding, resulting in black stool in the morning. 4. Tumors: for example, esophageal and stomach tumors, tumor erosion and ulcer necrosis can cause bleeding and lead to black stool. 5. Blood diseases: such as leukemia, hemophilia, thrombocytopenia, etc. can also cause gastrointestinal bleeding, resulting in black stool in the morning. There may be other reasons for black stool in the morning, so we suggest that the patient actively consult the doctor, improve the examination, clarify the cause of the disease, and promptly treat the symptoms to avoid further development of the disease.