Hello, my friend! Black stool means there is something wrong with your digestive tract. In particular, there is black stool, which is probably caused by gastrointestinal bleeding. Upper gastrointestinal bleeding, generally dark, black, and mixed with stool, medically known as tar stool. The common bleeding sites of upper digestive tract are: esophageal varices bleeding, gastric and duodenal ulcer bleeding, esophageal cancer, cardiac cancer, gastric cancer, cancer (gland) body destruction bleeding, biliary tract bleeding and so on. How much blood is there? Blood in the stool is characterized by black color, because red blood cells are destroyed by digestive juices, such as gastric juice, duodenal juice, bile, pancreatic juice and other liquids, and become non-blood cell organic substances. They are mixed with digested food and enter the small intestine and colon to be digested and absorbed. The blood mixed with food residue turns into stool and is excreted, so the ambassador turns black. Long-term hematochezia leads to anemia and the body's resistance decreases. Be sure to go to the hospital as soon as possible to find out the reason and treat it! I hope my answer can help you and I wish you a speedy recovery!