What is black stool due to?

Iron tablets and some medicines can darken bowel movements without causing bleeding. Foods with deep pigments may also change colour temporarily. Stool that is truly melaena is often black, sticky, shiny, and unusually strong-smelling because blood has been altered during digestion. Gastritis, Helicobacter pylori infection, and a peptic ulcer can irritate or damage the stomach or duodenum and may present with black stool. A colour change alone cannot identify the cause.

Think back to recent meals, iron supplements, bismuth-containing products, and other medicines. Do not stop a prescribed medicine without advice. If the stool is tarry, keeps recurring, or has no clear harmless explanation, arrange prompt medical assessment. A clinician may ask about pain, vomiting, dizziness, medicines, and bowel changes, then decide whether tests are needed.

Seek urgent medical help for black tarry stool with faintness, marked weakness, confusion, shortness of breath, severe abdominal pain, vomiting blood, or vomit resembling coffee grounds. These symptoms can accompany significant digestive-tract bleeding. Even without them, contact a clinician promptly if black stool is new and unexplained.

Ask whether your medicines or supplements can explain the colour, whether the stool looks like melaena, and which warning signs should prompt emergency care. Mention when it began, how often it occurred, and any stomach symptoms.