Treatment of H. pylori is often done with a quadruple therapy, a combination of a proton pump inhibitor and a bismuth agent and two antibiotics. In this case, after the patient takes a bismuth agent such as bismuth potassium citrate, the bismuth agent is converted to bismuth sulfide by the action of intestinal bacteria, which may cause the stool to become black. So the symptom of black stool after taking drugs for H. pylori is usually a normal phenomenon that occurs during treatment and is caused by the bismuth contained in the treatment drug, which can be relieved by itself. It should be noted that patients may also experience adverse reactions such as abdominal pain and diarrhea when applying H. pylori medications, which usually resolve on their own after stopping the medication or changing it. Also if the patient has recently consumed blood products or iron supplements it may also cause dark stools, which is a normal condition. However, if black stools continue to appear even after adjustment of treatment, one needs to be alert to abnormalities caused by gastrointestinal bleeding, such as bleeding from ruptured fundic varices, gastric ulcers, and other factors. It is necessary to actively improve the stool routine, biochemical examination and colonoscopy to clarify the cause. If the black stool symptoms are caused by disease factors, the original disease needs to be treated to relieve the symptoms.