There are two possibilities for the appearance of black stools when taking drugs to kill H. pylori: one is the black stool caused by the drug itself; the other is irritation of the gastrointestinal mucosa, which leads to bleeding in the digestive tract. Black stools appear with drugs to kill H. pylori, often due to the presence of bismuth citrate in the drug. Since the drug has the component of bismuth, the appearance of black stool is a normal reaction to the color of the drug itself that causes black stool. Another situation, is the class of antibiotic drugs such as metronidazole or amoxicillin capsules, stimulate to the mucosa of the gastrointestinal tract, causing edema, congestion and erosion of the gastrointestinal mucosa, which leads to black stools. This is very rare and is often a gastric ulcer or duodenal bulb ulcer, where the likelihood of gastrointestinal bleeding on top of the disease is higher.