Blood in stool (rectal bleeding)
Visible blood in or on the stool, on the toilet paper, or in the toilet bowl. Bright red blood usually comes from the lower bowel or back passage — often piles or a small tear — but it can also signal inflammation or, importantly, a growth, so persistent or unexplained bleeding always needs assessment.
What it means
Blood in the stool means bleeding somewhere in the digestive tract. The colour is an important clue to where it comes from. Bright red blood — on the paper, dripping into the bowl, or coating the stool — usually arises low down, in the rectum or anus, and the commonest causes are entirely benign: haemorrhoids (piles) and a small tear in the skin of the back passage (an anal fissure), both often linked to constipation and straining. But bright red bleeding can also come from higher up in the colon, from inflammation as in ulcerative colitis, from small pouches in the bowel wall (diverticular disease, which can bleed or become infected as diverticulitis), from infections, and — importantly — from bowel polyps or a bowel cancer. Darker blood mixed through the stool, or black tarry stools, suggests bleeding from higher up and is considered separately. Because the same symptom ranges from harmless piles to a serious growth, blood in the stool should never simply be assumed to be haemorrhoids, especially in older adults or when there are other symptoms. The pattern — the colour, whether it is mixed in or just on the surface, and any accompanying change in bowel habit, pain, weight loss or tiredness — guides how urgently it needs looking into.
Common causes
- Haemorrhoids (piles) — the commonest cause of bright red bleeding; often with straining or constipation.
- Anal fissure — a small tear, causing bright blood and pain on passing stool.
- Inflammatory bowel disease (ulcerative colitis, Crohn's) — blood often mixed with mucus and diarrhoea.
- Diverticular disease / diverticulitis — bleeding or infection from pouches in the bowel wall.
- Bowel polyps or bowel cancer — an important cause to rule out, especially with a change in bowel habit or weight loss.
- Gut infections (gastroenteritis).
Lab work-up approach
The cause of rectal bleeding is worked out mainly clinically — with an examination and, where indicated, a look inside the bowel (sigmoidoscopy or colonoscopy) — but blood tests support it. A full blood count and haemoglobin check for anaemia from blood loss, and ferritin for iron deficiency from chronic slow bleeding. Faecal calprotectin helps show whether inflammation (as in inflammatory bowel disease) is present. In many people a stool test for hidden blood and a colonoscopy are the key investigations, particularly to exclude polyps or cancer. Mediora.AI can surface a low haemoglobin and ferritin, or a raised calprotectin, that fits a bleeding or inflammatory bowel cause; new or persistent rectal bleeding needs a clinical assessment.
Tests Mediora.AI can interpret
Related conditions
Panels to consider
When to see a doctor
Do not ignore blood in the stool. A single episode of bright red blood with an obvious cause like a hard stool and known piles is common, but see a doctor for bleeding that is persistent, recurrent or unexplained — and promptly if the blood is mixed through the stool, comes with a change in bowel habit lasting more than a few weeks, weight loss, tummy pain, or tiredness, or if you are over about 50, as these raise the concern for a growth that needs excluding. Seek urgent care for heavy bleeding, passing a lot of blood, or feeling faint, dizzy or very unwell, and for black tarry stools. Rectal bleeding should never simply be assumed to be piles without assessment. Mediora.AI helps flag anaemia or inflammation from your results; the cause of the bleeding is established by your doctor.