What causes blood in stool?

Bright red blood on paper or the outside of stool can come from haemorrhoids or an anal fissure, especially with straining or pain during bowel movements. Blood mixed through stool, mucus, diarrhoea, cramps, or urgency can occur with ulcerative colitis or an infection such as amoebiasis. Polyps and bowel or rectal conditions can bleed without pain, so recurrence should be assessed. Dark, tar-like stool points to bleeding higher in the digestive tract and needs prompt medical advice.

The amount, colour, timing, bowel pattern, pain, fever, and medicines such as blood thinners are useful details. Do not assume the source from colour alone.

Contact a clinician about any unexplained or repeated bleeding. Note whether blood is on the paper, coating stool, mixed in it, or accompanied by mucus. Avoid straining and keep stools soft with appropriate fluids and fibre unless a clinician has advised otherwise. Assessment may include an examination, blood or stool tests, and further bowel evaluation; [Polyp Removal](/treatments/risk-reduction-and-prevention/polypectomy/) may be discussed if a polyp is found.

Seek urgent care for heavy or continuing bleeding, black tarry stool, faintness, severe abdominal pain, repeated vomiting, confusion, or marked weakness. Arrange prompt review for bleeding with unexplained weight loss, persistent change in bowel habit, anaemia symptoms, fever, or nighttime diarrhoea.

Ask whether the pattern fits [Haemorrhoids](/conditions/haemorrhoids/) or [Anal Fissure](/conditions/anal-fissure/), whether infection or inflammation should be checked, and whether bowel or rectal evaluation is needed.