Melena Stool Colors and What They Can Tell You Your stool color can carry important clues about digestion, diet, or even disease. Most shades are harmless, but some changes signal the need for What is the difference between tarry stools and black stools in terms of gastrointestinal (GI) bleeding? MALENA: Melena is the medical term for black, tarry stools caused by the presence of digested blood. It typically indicates bleeding in the upper gastrointestinal (GI) tract, such as the: Stomach Duodenum