What should you know about black grey stool?

Grey or green shading can appear when stool mixes with bile or coloured food. Iron and some medicines can make it look nearly black. The more concerning pattern is stool that is uniformly black, sticky, shiny or tar-like, especially with stomach pain or weakness. Gastritis, Helicobacter pylori infection and peptic ulcer may affect the upper digestive tract and can be relevant to this symptom, although appearance cannot establish the cause.

List recent meals, supplements and medicines, including non-prescription pain relief. Observe whether the change resolves and whether the stool is loose, hard or tarry. Arrange medical advice for unexplained or recurring black-grey stool. Keep taking prescribed medicines unless a clinician tells you otherwise.

Go to urgent care for tar-like black stool, vomiting blood, faintness, collapse, severe abdominal pain, breathlessness, a racing heartbeat or sudden weakness. These symptoms can occur with digestive bleeding and need prompt assessment.

Ask whether your stool description suggests bleeding, whether you need examination or testing, and which medicines could be contributing. Share any history of stomach irritation, ulcers or recent illness.