Fine black spots in the stool may be caused by dietary factors, medication factors, or gastroesophageal varices and other factors that lead to gastrointestinal bleeding. 1. Dietary factors: if you eat pig blood, duck blood, sheep blood and other foods, can be due to the food contains a large number of ferrous sulfate, which leads to fine black spots in the stool, in addition, eating black sesame seeds, dragon fruit and so on, can be due to the food is not digested completely, which leads to fine black spots in the stool. 2. Drugs: If you take bismuth colloidal bismuth, bismuth potassium citrate and other bismuth agents due to illness, it can also lead to fine black spots in the stool. 3. Gastrointestinal bleeding: it can be caused by varicose vein rupture bleeding, peptic ulcer, inflammatory bowel disease, etc. If the amount of bleeding is small, there can be fine black dots in the stool, and it can be accompanied by loss of appetite, pain in the liver area and other phenomena. In addition, there are many other causes of fine black spots in the stool, it is recommended to go to the hospital in time to exclude non-disease factors, and receive treatment as soon as possible.