What should you know about dark green almost black poop?

Green stool can occur after eating leafy vegetables or foods with dark colouring. It may also appear when stool moves quickly through the bowel, leaving less time for bile to change colour. Iron supplements and some medicines can make stool look very dark or green-black.

Black stool that is shiny, sticky, or tar-like is different from ordinary dark green stool. It can result from bleeding higher in the digestive tract, including problems associated with stomach inflammation or an ulcer. Gastritis, Helicobacter pylori infection, and peptic ulcer are possible conditions a clinician may consider, but stool colour alone cannot identify the cause.

Think back to recent foods, iron, bismuth-containing products, and medicines, and note whether the stool was genuinely black, sticky, or foul-smelling. Do not stop a prescribed medicine without advice. If the unusual colour lasts, recurs, or has no clear food or medicine explanation, arrange a medical assessment.

A clinician may examine you and arrange blood or stool testing. Bring a list of medicines and supplements, plus details about abdominal symptoms and bowel changes.

Seek urgent help for black tarry stool with dizziness, fainting, unusual weakness, breathlessness, vomiting blood, severe abdominal pain, or a fast heartbeat. Prompt assessment is also appropriate for repeated black stools, especially if you take medicines that can irritate the stomach or affect bleeding.

Ask whether the appearance is more consistent with food or supplements, or whether bleeding should be excluded. Tell the clinician about stomach pain, nausea, heartburn, recent medicines, iron use, previous ulcers, and any change in energy or bowel frequency.