Prolonged black stools may be caused by disease factors such as upper gastrointestinal bleeding, medication factors, and lifestyle. 1. Disease factors: when suffering from erosive gastritis, peptic ulcer, gastric fundus – esophageal varices and other diseases leading to upper gastrointestinal bleeding, it will cause black stool. 2. Drug factors: some people take iron, bismuth and so on for a long time, after the drugs into the body, the role of stomach acid may appear black substances, which in turn lead to black stool color. 3. Lifestyle: Due to excessive stress and unhealthy diet, the barrier function of the gastric mucosa may be affected, inducing gastrointestinal bleeding, which may lead to black stools. There are many reasons for long-term black stools, so it is recommended to go to the hospital in time for routine stools, gastroenteroscopy and other tests to determine the cause of the disease and then treat the cause.