Melena
（重定向自Melaena）
In medicine, melena or melæna refers to the black "tarry" feces that are associated with upper gastrointestinal bleeding. The black color is caused by the hemoglobin in the blood being altered by digestive chemicals and intestinal bacteria.
Iron supplements may cause a grayish-black stool that should be distinguished from the black, tarlike stool that occurs from bleeding ulcer.