What should you know about light black stool?

Iron tablets, bismuth-containing medicines and deeply coloured foods can darken stool. Stool caused by digested blood is often black, sticky or tar-like and may have a strong unusual smell. Bleeding can occur in the stomach or upper intestine, including with gastritis, Helicobacter Pylori Infection or a peptic ulcer, but colour alone cannot identify the cause.

A clinician may ask about medicines such as anti-inflammatory painkillers or blood thinners, abdominal symptoms, dizziness and recent foods. Testing may be needed even when there is no pain.

Check whether the change followed a new medicine or strongly coloured food, and note its texture and how often it occurs. Do not stop prescribed blood thinners without advice. Arrange prompt medical review if the stool remains black, looks tarry, or has no clear harmless explanation. Take a medicine list or photographs if they help describe the change.

Go to an emergency department for black tarry stool with vomiting blood, fainting, severe weakness, fast heartbeat, breathlessness, confusion or severe abdominal pain. These features can indicate significant blood loss. Urgent assessment is also needed if you feel light-headed or unwell while taking medicines that increase bleeding risk.

Ask whether your medicines or symptoms could explain the colour, whether you need blood or stool tests, and which warning signs require emergency care. Tell the clinician about ulcers, stomach inflammation, previous bleeding and all non-prescription medicines.