Common causes
Most of the time, blood in the stool comes from a problem in the anus or rectum rather than anywhere more serious. The colour and pattern of bleeding can offer clues, though a proper examination is needed to be sure.
- Piles (haemorrhoids): often bright red blood, usually on the toilet paper or coating the stool
- Anal fissure: a small tear that causes bright red blood, usually with sharp pain when passing stool
- Constipation and straining: hard stool can cause minor bleeding on its own
- Anal fistula or abscess: bleeding alongside persistent discharge, swelling, or pain
When it could be something more serious
Darker blood mixed into the stool, or black tarry stool, can point to bleeding higher up in the digestive tract and should be assessed promptly. Blood in the stool that comes with a change in bowel habit, unexplained weight loss, persistent fatigue, or a family history of colorectal cancer also warrants a proper check, particularly in people over 45–50.
None of this means the cause is serious; most of the time it isn't. These are simply the situations where seeing a doctor without delay matters most.
What to expect at a consultation
A doctor will usually start with a history and a physical examination, which may include a simple visual and digital examination of the anus and rectum. Depending on what's found, further assessment such as a proctoscopy or colonoscopy may be suggested to see further inside the bowel and confirm the cause.
Most causes of rectal bleeding are managed with simple, non-surgical measures. A minor procedure is only considered when needed, for example for piles or a fissure that hasn't settled with conservative treatment.
Frequently asked questions
Is blood in the stool always serious?
No. Most cases are due to common, treatable causes such as piles or a fissure. Still, any persistent or unexplained bleeding is worth having assessed, since only an examination can confirm the cause.
Does the colour of the blood matter?
It can be a useful clue. Bright red blood usually points to the anus or rectum, while darker or black stool can suggest bleeding higher in the digestive tract. Even so, a proper examination is needed to confirm the source either way.
When should I see a doctor urgently?
See a doctor promptly if bleeding is heavy, persistent, associated with a change in bowel habit or weight loss, or if you're over 45–50, even if you feel otherwise well.
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