Is blood in stool always serious?

Not always — haemorrhoids and anal fissures are common causes. But it can indicate polyps, inflammatory bowel disease, or colorectal cancer, so any rectal bleeding deserves medical assessment, particularly over age 40 or with weight loss or bowel habit change.

It often is, but that assumption is how colorectal cancer gets diagnosed late. Bright red blood does not exclude a more serious cause.

Examination is essential, and colonoscopy is warranted over age 40-45, or at any age with weight loss, anaemia, altered bowel habit or family history.