Black and Green Poop: Possible Causes

Green stool can occur after eating leafy vegetables or foods with green colouring. Bile also stays greener when stool moves quickly through the bowel, sometimes during diarrhoea. Iron supplements may make stool dark green or black, and bismuth products can turn it black.

The more concerning pattern is not simply a dark shade: it is stool that is black, shiny, sticky, and tar-like, especially with an unusually strong smell. Bleeding in the stomach or upper intestine may cause this appearance. Gastritis, Helicobacter pylori infection, and a peptic ulcer can be associated with upper digestive bleeding, but stool colour cannot diagnose any of them.

Think back over recent meals, supplements, and stomach remedies, and note whether the change settles when the suspected colour source is no longer present. Keep hydrated if stools are loose, using frequent sips of fluid unless a clinician has given you fluid restrictions.

Arrange medical advice if the black colour has no clear explanation, continues, or appears tarry. Share the timing, stool texture, bowel frequency, and every medicine or supplement you take. Avoid taking extra anti-inflammatory painkillers while waiting for advice.

Go to emergency care if black stool occurs with vomiting blood, coffee-ground vomit, fainting, dizziness, cold or clammy skin, unusual weakness, breathlessness, or severe belly pain. Green colour does not make these warning signs less serious. If you feel faint, ask someone else to take you or call emergency services.

Ask if your supplements or food could explain the colour, whether your stool should be checked for blood, and whether you need evaluation for gastritis, Helicobacter pylori infection, or a peptic ulcer. Mention diarrhoea, abdominal pain, nausea, tiredness, or a previous history of digestive bleeding.