Rectal bleeding: common to serious

Published 13 March 2026 ·Last reviewed 13 March 2026 by the editorial team ·How we create our content

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.

Common questions

What is the most common cause of rectal bleeding?

Hemorrhoids are the most common cause of rectal bleeding, particularly bright red blood associated with bowel movements. Anal fissures are the second most common cause. Together, these benign conditions account for the majority of rectal bleeding presentations.

How do I know if rectal bleeding is serious?

Features that suggest more urgent assessment include: dark or black blood, large volumes of blood, bleeding with a change in bowel habit, bleeding with unexplained weight loss, bleeding with abdominal pain, or any new rectal bleeding in someone over 50 or with a family history of bowel conditions. However, any rectal bleeding that concerns you deserves assessment.

When to seek care Heavy bleeding or feeling faint? Get emergency help now. Emergency: 911

Not sure how urgent it is? Get help today.

  1. Emergency

    Heavy bleeding, black tarry stools, feeling faint, severe pain or trouble breathing.

    Call 911 or go to the ER.

  2. Today

    Fever, pain getting worse, a hot swollen lump, or trouble passing urine.

    Call your doctor or go to urgent care.

  3. Soon

    Bleeding or bowel changes nobody has checked, or anything lasting 3 weeks.

    Book a doctor’s appointment.

Feeling overwhelmed? Call or text 988, any time.

See all the signs

For this topic, get medical advice if you notice:

  • 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

Recording how you feel is not the same as being checked. These are the signs that need a doctor’s attention.

Call 911 or go to the emergency room now if you have:

  • bleeding that will not stop, a lot of blood (the toilet water turns red, or you pass large clots), or any bleeding with feeling faint or dizzy
  • fainting, a racing heart or trouble breathing
  • confusion or slurred speech, extreme shivering, no urine in a day, or blotchy skin
  • sudden severe belly pain, or a swollen, hard belly with vomiting or not passing stool or gas
  • you cannot pass urine at all, or your bladder feels full and painful and you can’t empty it
  • redness, swelling or severe pain spreading quickly around your anus, genitals or groin, especially with a fever or feeling very ill
  • a fever with a painful swelling near your anus if you have diabetes or a weakened immune system (for example, from chemotherapy or transplant medicines)
  • black, tarry stools

Call your doctor or go to urgent care today (or the ER if you can’t be seen today) if you have:

  • a temperature of 100.4°F (38°C) or higher, chills, vomiting, or feeling generally unwell
  • pain that is getting worse over days, or severe pain that stops you sitting or sleeping
  • a hot, swollen or very tender lump near your anus or at the top of the crease between your buttocks, or foul-smelling discharge
  • trouble urinating
  • bleeding that is getting heavier or more frequent, or blood mixed into your stool
  • feeling much more tired than usual, looking pale, or getting out of breath more easily than you used to
  • not passing stool for several days, or new belly pain

Make an appointment with your doctor if:

  • you have never had these symptoms checked by a doctor or nurse — whatever your age
  • you have had rectal bleeding for more than 3 weeks
  • your bowel movements have been looser, thinner or more frequent than usual for 3 weeks or more, or you have lost weight without trying
  • symptoms have not settled after a week or so, or keep coming back
  • you notice a new lump near your anus, between your buttocks or in your belly, or an itch or discharge that does not clear
  • you have new leakage or trouble controlling your bowels
  • you are 45 or over, or have a family history of bowel cancer or inflammatory bowel disease, and any of these symptoms are new for you

If you are unsure, it is always reasonable to ask. If things feel overwhelming, call or text 988 (Suicide & Crisis Lifeline) or chat at 988lifeline.org, any time. If you don’t feel safe, call 911.

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Discreet symptom tracking

Symptoms that come and go? Keep track, day by day.

For hemorrhoids, fissures, fistulas and other anal and rectal problems. A short, discreet email asks how things have been, and saves each answer, so you can look back at every flare and every good week in your own words. If you haven’t had your symptoms checked, see your doctor first.

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  • Each Sunday, a link to your week, ready for your next appointment.
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Hemorrhoid bleeding: how much is too much

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