Diarrhea with black, watery stool

Stool that is black, sticky, tar-like, or unusually foul-smelling may be melaena, caused by digested blood from the stomach or upper bowel. Gastritis, Helicobacter pylori infection, and a peptic ulcer are possible sources. Iron tablets, bismuth-containing products, and some dark foods can also change stool colour, but watery diarrhea makes it difficult to judge the cause by appearance alone.

Pay attention to dizziness, weakness, shortness of breath, faintness, upper-abdominal pain, or vomiting that looks like coffee grounds. These can accompany significant blood loss and should not be watched at home.

Contact urgent medical services or an emergency department for advice today, and explain that the stool is black and watery. Do not drive yourself if you feel faint or weak. Bring a list of medicines and supplements, including iron, aspirin, or anti-inflammatory painkillers, and note when the change began.

Take only small sips of fluid if you can drink safely. Do not take anti-diarrhea medicine or anti-inflammatory painkillers unless a clinician tells you to. Do not assume a dark food explains tarry stool.

Call emergency services for fainting, confusion, cold or clammy skin, severe weakness, rapid deterioration, vomiting blood or coffee-ground material, severe abdominal pain, or inability to keep fluids down. Even without these signs, new black watery stool requires prompt assessment.

Could this be bleeding, a medicine effect, or another digestive problem? Do I need blood tests, stool testing, or an examination of my stomach? Which medicines should I avoid until the cause is clear?