Drinking black tea causes hematochezia, which is usually caused by bleeding in the digestive system. If the patient has gastritis, gastric ulcer, duodenal ulcer, etc., the gastric mucosa is damaged, and when drinking strong tea, stimulating the gastric mucosa will lead to bleeding. If the patient's bleeding volume is small, black stool will appear when blood is oxidized in the intestine and mixed with feces. If the patient has a large amount of bleeding and a fast speed, it will show bright red stool. At the same time, lower gastrointestinal bleeding can also cause hematochezia, such as hemorrhoid bleeding and intestinal polyp bleeding.