Black and shiny stools may be caused by medication, food and gastrointestinal bleeding. 1. Drug factors: black stools caused by drugs are usually not shiny, such as taking iron, bismuth potassium citrate, etc. Black stools can occur. 2. Food factor: after consuming a large amount of food made from animal blood such as pig’s blood, duck’s blood, chicken’s blood, etc. for a short period of time, the iron in the blood cells will be oxidized, forming black compounds mixed in the stool and making the stool black. 3. Gastrointestinal bleeding: gastric ulcers, duodenal ulcers, stress ulcers, esophageal ulcers and so on may have bleeding from the ulcer surface. Tumors such as esophageal and stomach tumors, leukemia, hemophilia, thrombocytopenia and so on can also cause gastrointestinal bleeding, leading to the occurrence of black stools. There may be other reasons for dark and shiny stools, and you can go to the hospital for examination to clarify.