What should you know about black blood in stool?

Stool that is jet black, sticky, or has a tar-like appearance may indicate bleeding higher in the digestive tract, because blood becomes darker as it is digested. Dark stool can also follow iron tablets, bismuth-containing medicines, or strongly coloured foods, so appearance alone cannot identify the cause.

Bleeding from the bowel can occur with inflammatory conditions such as Crohn's Disease or Ulcerative Colitis, growths such as bowel or rectal cancer, or other digestive problems. A clinician may ask about medicines, recent illness, abdominal symptoms, and changes in bowel habit before deciding whether tests are needed.

If the stool is genuinely black and tarry, contact a healthcare professional promptly and describe its colour, texture, and when it began. Mention iron, bismuth, aspirin, anticoagulants, or anti-inflammatory medicines, and do not stop a prescribed medicine without medical advice.

If possible, keep a note of any further stools and associated symptoms. Avoid treating unexplained bleeding with leftover medicines. Assessment may include an examination, blood tests, or a bowel investigation chosen according to your symptoms and medical history.

Seek emergency help for heavy or ongoing bleeding, fainting, marked dizziness, confusion, severe abdominal pain, vomiting blood, breathlessness, or unusual weakness. These features can signal significant blood loss or another acute problem.

Do not wait for a routine appointment if black stool recurs or is accompanied by a fast heartbeat, pale or clammy skin, or difficulty staying awake. If you feel faint, lie down safely and have someone help you obtain urgent care.

Ask what causes are most relevant given your medicines and symptoms, whether you need blood tests or a camera examination, and which warning signs should prompt immediate return. You can also ask whether a recent food or medicine could explain the colour.