Black stool after colonoscopy may be related to diet, medication and intestinal bleeding. For black stools caused by diet and medication, basically no treatment is needed; for black stools caused by intestinal bleeding, we should intervene with medication such as omeprazole, growth inhibitor and surgical treatment. 1. Influence of diet: After gastroenteroscopy, black stools can appear when consuming iron-rich foods such as duck blood and pig’s blood. This phenomenon is a normal physiological phenomenon and does not require any treatment. 2. Drug effects: after gastroenteroscopy, taking bismuth pectin, ferrous sulfate and other drugs can also lead to black stools. This is also a physiological phenomenon and does not require treatment. 3. Intestinal bleeding: improper operation during colonoscopy can lead to gastrointestinal bleeding, which can also lead to the symptom of black stool. The site of bleeding should be clarified through enteroscopy, and hemostatic drugs such as omeprazole and growth inhibitor can be used in time for treatment. After taking the drug, patients may experience adverse reactions such as drug rash, nausea and vomiting. Allergy or hypersensitivity to the drug and pregnant women should be prohibited from using this drug. For patients with serious conditions, endoscopic hemostasis or surgical hemostasis can also be taken. This kind of black stool after gastroenteroscopy should be taken seriously, consult a doctor to confirm the diagnosis, and follow the doctor’s instructions for treatment.