Black stool after taking cephalosporin is considered to be related to dietary factors, chronic gastritis, peptic ulcer and so on. 1. Dietary factors: oral cephalosporin at the same time, eating animal blood products, such as pig’s blood, duck’s blood, etc., black stools can occur, stop eating these foods, generally can return to normal. 2. Chronic gastritis: due to the existence of chronic inflammation of the gastric mucosa, after taking cephalosporin orally, it will further stimulate the gastric mucosa, causing bleeding, and the blood is discharged into the intestinal tract and mixed with feces, which can cause black stools. 3. Peptic ulcer: mainly including gastric ulcer and duodenal ulcer, due to the presence of ulcerated surface of the gastric and duodenal mucosa, after taking cephalosporin orally, it can stimulate the ulcerated surface to cause hemorrhage, and the blood oxidized to form sulfur, which will lead to black stool. If you exclude dietary factors, black stool persists, it is recommended to consult a doctor in a timely manner, under the guidance of a professional physician to identify the cause of the disease, and comply with the doctor’s instructions for treatment.