The color of stool is pale yellow, yellow or slightly dark yellow under normal circumstances. In normal people, bilirubin in the bile is broken down by bacteria at the end of the ileum and colon into fecal bilogen, which is partially reabsorbed by the intestine into the enterohepatic circulation, and mostly oxidized in the colon into fecal bile, which is excreted in the stool, so the stool is yellow due to the presence of fecal bile. If bile excretion is obstructed, including intrahepatic biliary stasis and extrahepatic biliary stasis, the stool will be white clay in color, suggesting the presence of biliary obstruction. If the stool is dark, tarry black, it suggests the possibility of gastrointestinal bleeding, such as gastric ulcers and duodenal ulcers. In addition, if abnormal pigments are mixed with diet and medications that are not destroyed, abnormal stool color may also occur, such as eating animal liver, blood products, or taking oral iron supplements, the stool may appear black. Eating large amounts of protein, such as eggs and milk, the stool may appear brown, and eating foods containing a lot of chlorophyll, chlorophyll preparations, etc., the stool may appear green. Therefore, if abnormal stool color manifests and persists even after adjusting the dietary structure, you should promptly consult a doctor, improve relevant tests for differential diagnosis, and then provide symptomatic treatment according to the cause.