What Does It Mean If My Poop Is Black? Melena Guide A change in the colour of one's stools may sometimes be due to dietary changes; though it could also reveal something about one's health. Where stool appears or , it Black, tarry stools are NOT normal. They could be a sign of Melena upper gastrointestinal bleeding that requires urgent medical attention. Learn the difference between Melena vs Hematochezia, common 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 cause of recurrent melena stool with multiple telangiectasia and prominent veins in the proximal ascending colon in a 14 year old boy?