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 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 Hematochezia vs melena: Comparing symptoms, causes, and treatment Know Your Stool Physiology Video USMLE Step 1