Black Stool and Liver Problems: What to Know

Melaena, also called tarry stool, is often jet black, sticky and unusually strong-smelling. It can happen when blood is digested as it travels from the stomach or upper small intestine. Common sources include an irritated stomach lining, a peptic ulcer or inflammation related to Helicobacter pylori infection.

The stool colour does not by itself show that the liver is the source. In advanced liver disease, high pressure in veins around the liver and reduced production of clotting proteins can make digestive-tract bleeding more likely or harder to stop. Iron tablets, bismuth-containing medicines and some foods can also darken stool without causing bleeding, but a new tarry change should still be checked.

Contact a clinician promptly if your stool is black and tarry, especially if you have known liver disease, previous ulcers, or take medicines that affect clotting. Tell them when the change began, how often it has happened, and whether you have taken iron, bismuth, aspirin or an anti-inflammatory painkiller. Do not stop a prescribed medicine without medical advice.

A clinician may check your blood pressure, pulse, abdomen and blood count, and may arrange stool testing or an upper endoscopy to find bleeding. Until you are assessed, avoid alcohol and avoid taking extra aspirin or anti-inflammatory painkillers unless a clinician has specifically advised them.

Go to an emergency department now for black stool with vomiting blood or material that resembles coffee grounds, fainting, confusion, severe weakness, shortness of breath, cold or clammy skin, or severe abdominal pain. These signs can accompany significant blood loss.

If you have cirrhosis or another serious liver condition, treat black tarry stool as urgent even if you feel reasonably well. Seek emergency help if you also develop increasing abdominal swelling, yellowing of the skin, unusual sleepiness or new confusion.

Ask what could explain the stool colour, whether your liver condition changes your bleeding risk, and whether you need blood tests or an endoscopy. Share a complete list of medicines and supplements, including non-prescription painkillers and iron.