What does greenish-black stool mean?

Dark green vegetables, food colouring, iron supplements, and some medicines can change stool colour. A faster bowel transit time can leave bile looking green rather than brown. These causes are often temporary, especially when you otherwise feel well.

Black stool that looks sticky, shiny, or tar-like is different. It can indicate digested blood from the upper digestive tract. Gastritis, a peptic ulcer, or Helicobacter Pylori Infection can be associated with upper digestive bleeding. Colour alone cannot identify the cause.

Think back over the last day or two: note foods, iron, bismuth-containing products, and any new medicines. Do not stop a prescribed medicine without advice. If the colour returns to normal after a likely food or supplement trigger and you feel well, keep observing and record any recurrence.

Arrange medical advice if dark stools continue, recur without an obvious trigger, or occur with stomach pain, nausea, dizziness, unusual tiredness, or vomiting. A clinician may ask about medicines and arrange stool or blood tests.

Seek urgent medical care for black tarry stool, visible blood, vomiting blood or material resembling coffee grounds, fainting, marked dizziness, confusion, severe abdominal pain, or difficulty breathing. These features can signal significant bleeding or another acute problem.

When did the colour change begin, and could iron, food, or a medicine explain it? Does the stool look tarry or sticky? Do my symptoms or medicines make bleeding more concerning? What tests should check the digestive tract or blood count?