Rectal bleeding: common to serious

At a glance

Rectal bleeding has many possible causes, ranging from very common and benign to uncommon and serious. Understanding this range helps put the symptom in context — but it does not replace clinical assessment. Only a clinician can determine the cause of your bleeding through examination and, if needed, investigation.

This guide arranges the causes from most common to least common, providing context without diagnosis.

Very common causes

Hemorrhoids

The most frequent cause of rectal bleeding:

  • Bright red blood on toilet paper, on the stool surface, or in the toilet bowl
  • Often painless (internal hemorrhoids) or associated with a painful lump (external/thrombosed)
  • Typically associated with straining, constipation, or prolonged sitting
  • Affects a significant proportion of the adult population at some point

Anal fissure

The second most common cause:

  • Bright red blood associated with sharp pain during bowel movements
  • Often a small amount of blood — streaks on paper or stool
  • Commonly triggered by hard stools or constipation
  • Tends to follow a recognisable pattern of pain-then-burning

Common causes

Rectal/colorectal polyps

Benign growths on the lining of the colon or rectum:

  • May bleed painlessly
  • Often discovered during investigation for bleeding
  • Removed during colonoscopy as a precautionary measure
  • Most are non-cancerous but some types carry a risk of developing into cancer over time

Diverticular disease

Outpouchings in the colon wall that can bleed:

  • Can cause sudden, painless, sometimes significant bleeding
  • More common in older adults
  • The bleeding often stops on its own but may recur
  • Sometimes requires hospital assessment if heavy

Inflammatory bowel disease (IBD)

Crohn’s disease and ulcerative colitis:

  • Bleeding typically mixed with stool, often as bloody diarrhoea
  • Accompanied by other symptoms — urgency, frequency, abdominal pain, weight loss
  • Usually presents with a cluster of symptoms rather than bleeding alone
  • Diagnosed through colonoscopy and biopsy

Proctitis

Inflammation of the rectal lining:

  • Can be caused by IBD, infection, radiation, or other factors
  • Bleeding often accompanied by urgency, mucus, and rectal pain
  • Diagnosed through examination and sometimes biopsy

Less common causes

Angiodysplasia

Abnormal, fragile blood vessels in the colon wall:

  • More common in older adults
  • Can cause painless, sometimes significant bleeding
  • Diagnosed through colonoscopy
  • Treatable with cauterisation

Rectal prolapse

Protrusion of the rectal wall through the anus:

  • Bleeding from friction and irritation of the prolapsed tissue
  • Usually accompanied by the sensation of tissue protruding
  • Diagnosed by clinical examination

Solitary rectal ulcer

An ulcer on the rectal wall, often associated with straining:

  • Can cause bleeding, mucus, and pain
  • Associated with defaecation disorders
  • Diagnosed through colonoscopy and biopsy

Uncommon but important causes

Colorectal cancer

While less common than the causes above, colorectal cancer is the concern that most people worry about:

  • Can cause rectal bleeding that may be bright red or dark
  • Often accompanied by other symptoms: change in bowel habit, unexplained weight loss, fatigue, abdominal pain
  • More common with increasing age, particularly over 50
  • Family history significantly affects risk
  • Highly treatable when caught early through screening and investigation

Risk factors that increase concern

Any rectal bleeding warrants assessment, but the following features increase the importance of prompt investigation:

  • Age over 50 (or younger with a significant family history)
  • A persistent change in bowel habit alongside the bleeding
  • Unexplained weight loss
  • Fatigue or symptoms of anaemia
  • Dark blood mixed through the stool
  • Abdominal pain or a mass
  • Family history of bowel cancer or polyps

The perspective

The vast majority of rectal bleeding is caused by hemorrhoids and fissures. This is statistically true and important to remember when anxiety is high.

But statistics describe populations, not individuals. The only way to know what is causing your bleeding is to have it assessed. The process — a GP visit, an examination, and possibly further investigation — is straightforward and provides the certainty that neither reassurance nor worry can offer.

Getting checked is sensible. It is not overreacting. It is the responsible thing to do.

When to seek care

If you experience any of the following, seek urgent medical care:

  • Heavy bleeding that will not stop
  • Dark or black stool
  • Bleeding with dizziness or faintness
  • Bleeding with severe abdominal pain
  • Bleeding with unexplained weight loss
  • New rectal bleeding over age 50

Explore more

Related guides

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Hemorrhoid bleeding: how much is too much

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