When should you see a doctor about black stools?

Black, tar-like, sticky stools can indicate digested blood from higher in the digestive tract. Gastritis, Helicobacter pylori infection, and peptic ulcer are possible causes. Iron tablets, bismuth-containing medicines, and some dark foods can also change stool colour. A clinician needs the full history to distinguish these possibilities, particularly if the change is new.

Note the stool’s colour and texture, when the change began, and any medicines or supplements taken. Record abdominal pain, nausea, vomiting, dizziness, breathlessness, or unusual tiredness. Do not stop prescribed medicine without advice, but tell the clinician about every product you use. If possible, arrange assessment promptly rather than waiting for repeated episodes.

Get emergency help for black stools with fainting, severe dizziness, confusion, cold clammy skin, rapid weakness, vomiting blood, severe abdominal pain, or breathlessness. Seek same-day medical advice for recurrent tarry stools, especially if you take medicines that affect bleeding or have a history of digestive ulcers. A clinician may need to assess for blood loss and the source of bleeding.

Ask whether the colour could be caused by a medicine or food, whether blood loss needs testing, and which warning symptoms should send you directly to emergency care.