It is normal for stool to be black and then yellow. The normal color of stool is yellowish-brown, and there are physiological and pathological reasons for darkening. Physiological reasons are mainly due to the consumption of animal liver, green leafy vegetables and other foods, or taking iron-containing drugs, in this case, once you stop eating food or drugs, the color of the stool can return to normal. If the color of the stool becomes dark, even black, and oily this may be due to pathological causes, gastrointestinal disorders, or suffering from gastrointestinal digestive bleeding. If the cause is physiological, no intervention can be made. If it is due to pathological causes, symptomatic treatment is required. If it is due to gastrointestinal dysfunction, timely adjustment should be made. If it is caused by gastrointestinal and other gastrointestinal bleeding disorders, immediate hemostatic disposition should be performed, hemostatic drugs should be used, and in severe cases, immediate surgical treatment should be performed.