Dark brown poop is generally within the normal range, but some changes in stool color deserve attention. Brown stool naturally varies in shade, and color alone doesn't tell you much about your health.
Black, tarry stool is different, and knowing what to look for can help you recognize when to seek medical attention.
What Makes Poop Brown?
Bile carries bilirubin, a pigment formed when old red blood cells break down, into the intestine. Bacteria in the colon convert it into stercobilin, which colors stool brown.
Less bile pigment reaching the intestine makes stool paler. Digested blood and certain medicines can make it appear black.
Is Dark Brown Poop Normal?
Yes. Brown is the normal stool color, and shade alone is not a reliable sign of a health problem. There is no clear clinical cutoff separating normal dark brown from abnormal brown.
The more important change is when stool becomes black. Melena, meaning black and tarry stool, usually indicates bleeding in the upper digestive tract.
Blood darkens as it travels through the digestive system, and black stool may continue for days after bleeding stops.
Stool returning to its usual color does not prove that bleeding has stopped or rule out a previous bleed. Color is a clue, not a way to confirm or exclude bleeding.
Which Medicines Can Darken Stool to Black?
Two common products turn stool black on their own, and what separates them from bleeding is everything other than the color.
Iron and bismuth. Both iron supplements and bismuth can turn stool black without bleeding. Bismuth is the active ingredient in Pepto-Bismol.
Melena is typically tarry. Bleeding-related stool is often black, sticky or tar-like, and unusually strong-smelling. Stool without those features is less typical of melena, though appearance alone cannot rule out bleeding.
If you take iron or bismuth and feel well, mention the change to your healthcare provider. But do not assume medication explains new black stool. Black, tarry stool warrants urgent medical evaluation, even if you take these medicines. If you also feel faint, have significant weakness or shortness of breath, or are vomiting blood, seek emergency care.
