What should you know about black constipated stool?

Constipation usually refers to hard stools, straining, or bowel movements that are less frequent than your normal pattern. It does not by itself explain a black, sticky, tar-like appearance. Digested blood from a peptic ulcer, gastritis, or Helicobacter pylori infection can create that appearance.

Iron tablets and bismuth medicines may darken stool while constipation makes it harder to pass. Dark foods can also alter colour. Look for the combination of colour, texture, smell, pain, and general symptoms rather than relying on constipation alone.

If stool is hard but normally brown, use your usual constipation plan and maintain fluids unless a clinician has restricted them. If it is black and tarry, contact a healthcare professional promptly. Mention straining, abdominal symptoms, recent medicines, and whether the change happened before or after constipation began. Do not use extra anti-inflammatory pain medicine for discomfort without advice.

Seek emergency care for black stool plus fainting, severe weakness, confusion, breathlessness, vomiting blood, severe abdominal pain, or a racing heartbeat. Same-day medical review is appropriate for repeated tarry stool, even when constipation is also present.

Ask whether the stool looks like melaena, whether a medicine is contributing to both darkness and constipation, and whether tests for gastritis, Helicobacter pylori infection, or peptic ulcer are suitable.