Does bowel cancer cause blood in stool?

Bleeding from higher in the bowel may make stool look dark or tarry, while bleeding nearer the rectum can appear bright red on the paper, in the bowl, or mixed with stool. Bowel cancer may also cause a change in bowel habit, narrower stools, abdominal discomfort, tiredness, or unexplained weight loss. These features do not identify the cause on their own; piles, anal fissures, inflammation, polyps, and infection can also bleed.

Arrange a medical assessment for new, repeated, or unexplained blood in stool. A clinician may ask about the colour and amount of blood, bowel changes, medicines, and family history, then decide whether an examination, stool test, blood test, or further bowel investigation is appropriate. Keep a note of when bleeding occurs and whether it is mixed with stool.

Seek urgent help if bleeding is heavy or continuing, stool is black and tarry, or you feel faint, confused, unusually weak, or short of breath. Severe abdominal pain, repeated vomiting, or a swollen abdomen also needs prompt assessment.

Ask what the colour and pattern of bleeding might suggest, which tests are suitable, and whether your bowel habit or family history changes the assessment. Ask when to return if the bleeding stops but then comes back.