Pitch-black stool: what to know

Black stool that is tar-like, sticky or unusually foul-smelling can be melaena, caused when blood is digested as it passes through the stomach or small intestine. Gastritis, a peptic ulcer or Helicobacter Pylori Infection can contribute to upper digestive bleeding. Iron tablets, bismuth-containing medicines and strongly coloured foods may also darken stool, but appearance alone cannot reliably distinguish the causes. Tell a clinician about abdominal pain, vomiting, dizziness, weakness, faintness and medicines such as aspirin or anti-inflammatory painkillers.

Contact a healthcare service promptly if the stool is genuinely pitch-black or tarry, particularly if it is new or repeated. Keep the medicine packaging or a list of everything you take, and note when the change began. Do not stop a prescribed medicine without advice. A clinician may check your circulation, blood count and abdomen and may recommend tests to find the source.

Go to emergency care for black stool with fainting, severe dizziness, confusion, cold clammy skin, rapid heartbeat, severe abdominal pain, vomiting blood or vomit that looks like coffee grounds. These signs can indicate significant bleeding or shock and should not wait for a routine appointment.

Could my medicines or supplements explain the colour? Do my symptoms suggest Gastritis, a Peptic Ulcer or Helicobacter Pylori Infection? Which tests should be arranged, and what should I do if the stool changes again?