Functional dyspepsia does not usually cause black stools. Black stools usually indicate the presence of gastrointestinal bleeding, usually caused by organic diseases of the gastrointestinal tract, benign diseases including duodenal ulcer, gastric ulcer and gastritis, and malignant diseases including gastric cancer and colorectal cancer. If the patient is >40 years old and is accompanied by wasting, anaemia or has a family history of gastrointestinal tumours, the possibility of organic diseases of the gastrointestinal tract should be noted and prompt medical treatment is recommended.