Black stools are mainly caused by bismuth potassium citrate or bismuth pectin, sometimes the tongue will be black, after stopping the drug will return to normal, this situation is not to worry. The course of treatment of quadruple bactericidal therapy is usually 10-14 days, it is not recommended to take long-term, especially bismuth, it will have some damage to liver and kidney function. In addition, during the treatment period should pay attention to a light, easy-to-digest diet, should not eat cold, stimulating food, to drink more water.