The black stool after taking medication for H. pylori is not only related to the presence of bismuth pectin in the medication, but some people may have eaten iron-rich foods that cause it. Because H. pylori infection is treated with a combination of medication-based treatment, the use of drug therapy will add bismuth potassium citrate or bismuth pectin. The addition of bismuth to these two drugs will have an effect on the color of the stool, and darkening of the stool is a common manifestation. Although the color of the stool is black, but there will be no diarrhea, abdominal pain and other symptoms. Some people prefer to eat animal blood and animal offal in their diet, which is particularly rich in iron. Iron in the digestive system and digestive fluid oxidation reaction, so that the color of the stool appears black phenomenon. However, some people have black stools accompanied by abdominal pain and diarrhea, so they should be alerted to upper gastrointestinal bleeding, and need to be diagnosed and treated with routine stool tests.