What should you know about black liquid stool causes?

Liquid stool can occur when the bowel moves contents quickly, allowing less water to be absorbed. A black colour may follow iron supplements, bismuth-containing products, or strongly coloured foods. Another possibility is melaena: blood exposed to digestive juices can become black and make stool sticky, loose, or liquid. Gastritis may irritate the stomach lining, while a peptic ulcer can bleed. Helicobacter pylori infection is one condition that can be associated with ulcer disease. The appearance is useful information, but it cannot identify the cause on its own.

Record when the change began, how often it has happened, and whether it looks tarry or has an unusually strong smell. Keep the names of medicines and supplements available for the clinician, including pain relievers. Drink small amounts of fluid if you are losing liquid stool and can keep them down, but do not use anti-diarrhoeal medicine to delay assessment of unexplained black stool. Contact a healthcare professional promptly when the colour cannot be explained by something you ate or took.

Call emergency services for black liquid stool with fainting, severe weakness, confusion, rapid breathing, cold sweaty skin, severe abdominal pain, or blood vomit. These symptoms may accompany substantial internal bleeding or dehydration. Seek urgent assessment as well if liquid stool continues and you cannot keep fluids down, pass very little urine, or become increasingly light-headed. A person who feels faint should sit or lie down and should not travel alone.

Could a supplement or medicine account for this colour? Does the stool look like melaena? Should I be checked for gastritis, peptic ulcer disease, or Helicobacter pylori infection? How can I replace lost fluid safely?