Hi, Black stool may be a sign of some diet (iron supplements for example) but also it may be caused due to the passage of blood in stool and then it is called melena. The most common cause of melena is peptic ulcer disease. However, any bleeding within the upper gastrointestinal tract or the ascending colon can lead to melena. Melena may also be a complication of anticoagulant medications, such as warfarin. Diagnosis of disease after patient having melena is important. For this laboratory stool examination, upper GI endoscopy and barium X-ray helps the medical attendant to find the cause. Treatment will depend on the cause. In case of peptic ulcer, conservative line of treatment will heal the ulcer, bland diet, medications for H.pylori infection will cure it. In every case, I would not ignore it and tests are necessary. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Ivan R. Rommstein, General Surgeon