The color of normal stool is generally yellow, light brown or dark brown. No matter how thick or thin the stool is, if it appears black, from light ink black to tar-brown black, it is called black stool. Generally speaking, the presence of black stool indicates that there is bleeding in the upper gastrointestinal tract, we will call it “true black stool”. However, some black stools, but not due to bleeding, such as taking iron supplements, bismuth and activated carbon powder (tablets) for the treatment of stomach diseases, some Chinese medicine, and eating animal blood such as sheep blood, pig blood, etc.. These black stools are not caused by bleeding, so we will call them “false black stools”. After bleeding from the upper gastrointestinal tract, the blood flows out in the esophagus, stomach and intestines to decompose iron, which combines with the sulfide produced by bacteria to form iron sulfide and appears black. Therefore, black stools can also appear after eating animal blood and iron supplements for this reason. So we have to distinguish carefully. 1, true black stool: especially in larger amounts, bright black, most like asphalt used for paving, most patients have a history of disease, such as stomach pain, ulcer disease, cirrhosis of the liver, or have taken certain anti-inflammatory drugs that hurt the stomach. Patients may have symptoms such as panic, rapid heart rate, fainting, and pallor (only in severe cases). However, a very small number of patients do not have symptoms, such as the above-mentioned onset of Li Ji. 2, false black stool: black is mostly dark gray, dark black, except for having eaten animal blood, rarely shiny, with a history of taking drugs or eating blood products. Pulling black stool for more than 3-4 days, without any other symptoms. What does true black stool mean 1. It means there is bleeding in the upper gastrointestinal tract. The upper gastrointestinal tract is the section from the esophagus to the duodenum (including the stomach). Lower GI bleeding may also produce black stools if it is in the intestinal tract for a long time, but this is very rare. 2. It means that the amount of bleeding is at least 60 ml, which is no longer hidden but called explicit bleeding. As for the amount of bleeding, it is not easy to identify, especially when the black stool has not yet been excreted, and even the doctor is a little confused. Generally speaking, the more black stools are removed, the more dilute they are, and the more frequent they are, the more bleeding there is. In addition, those who have dizziness, fainting, fast heartbeat, low blood pressure, pale face, cold hands and feet, and little or no urination indicate a lot of bleeding. When there is a lot of bleeding, of course, anemia will occur, although it is often found later.