Taking quadruple drugs for H. pylori does not usually cause blood in the stool, it may cause black stool because of the bismuth agent. Quadruple drugs are often used to eradicate Helicobacter pylori, specifically 4 drugs: 1 proton pump inhibitor + 1 bismuth + 2 antibiotics, such as esomeprazole magnesium enteric coated tablets + colloidal bismuth pectin + amoxicillin + furazolidone. Among them, the bismuth agent can have a chemical reaction with hydrogen sulfide in the intestines to produce black-colored iron sulfide, which in turn makes the color of feces black, which is a normal phenomenon. Therefore, taking the quadruple medication for H. pylori eradication will result in black stools. If the black stools are caused by bismuth, it is generally not recommended to stop taking the medication. Specific medication should be guided by a specialist, and should not be used without authorization. If discomfort occurs, it is necessary to seek medical treatment as soon as possible.