Blood in stool: color guide, causes and when to see a doctor

Rectal bleeding: Is it haemorrhoids or a sign of bowel cancer?

Used sheet of bloody toilet paper and a roll on white background, haemorrhoids and rectal bleeding concept.

It can feel both frightening and taboo to discover blood in the toilet bowl or on the paper after a bowel movement. But the fact is that rectal bleeding is a very common symptom that most people experience at some point in their lives.

Although the cause is often harmless - such as haemorrhoids - it is crucial never to ignore it. In this guide, we review the most common causes, the difference between symptoms, and why a bowel examination is your most important safeguard against bowel cancer.

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Why am I bleeding from the rectum?

There can be many causes of rectal bleeding. The colour of the blood and accompanying symptoms can often provide a clue as to where the bleeding originates.

1. Haemorrhoids (The most common cause)

Haemorrhoids are swollen blood vessels in or around the rectum (resembling small varicose veins). They typically bleed with fresh, bright red blood, which is seen on the surface of the stool or on the toilet paper.

• Symptoms: Itching, stinging, and a sensation of a lump at the anal opening.
• Severity: Harmless, but bothersome.

2. Anal Fissure (Tear at the anus)

A small tear in the lining of the anus, often caused by hard stools or constipation.

• Symptoms: Sharp, stabbing pains during and after bowel movements, along with fresh blood.

3. Bowel Cancer (Colorectal cancer)

This is the most serious cause. In this case, the blood is often darker and can be mixed into the stool itself.

• Symptoms: Changed bowel habits (alternating constipation and diarrhoea), unexplained weight loss, fatigue, and abdominal pain.
• Severity: Serious, but has a good prognosis if detected early.

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When should I see a doctor?

The rule is simple: Rectal bleeding should always be investigated by a doctor the first time it occurs.

Even if you have had haemorrhoids before, new bleeding can mask other conditions. You should seek medical attention promptly if:

• Your stool changes shape or frequency for more than 4 weeks.
• You feel that the bowel is not emptying properly.
• The blood is dark or mixed with mucus.
• You feel unusually tired (signs of iron deficiency/anaemia).

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Bowel examination: What can I expect?

Many fear a bowel examination, but modern methods are quick and associated with minimal discomfort. The examination is the only way to get certainty.

1. Physical examination: The doctor feels with a finger (digital rectal examination) to check for haemorrhoids or lumps near the opening.
2. Endoscopy (Sigmoidoscopy or Colonoscopy): A thin, flexible tube with a camera is inserted into the bowel. Here, the doctor can see the lining directly and remove any polyps (precancerous growths) before they develop further.
3. Stool sample (FIT test): A test that checks for invisible blood in the stool.

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Prevention: Look after your bowel

You can reduce the risk of both haemorrhoids and bowel cancer through your lifestyle:

• High-fibre diet: Eat plenty of whole grains, vegetables, and fruit.
• Drink water: It keeps the stool soft and prevents tears.
• Physical activity: Exercise stimulates bowel movement (peristalsis).
• Go when you need to: Do not hold it in; this increases pressure in the rectum and can cause haemorrhoids.

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Sources and scientific background (PubMed)

To ensure correct information, we rely on the latest research and clinical guidelines:

• On frequency of haemorrhoids vs. cancer: Lohsiriwat V. "Hemorrhoids: From basic pathophysiology to clinical management." World J Gastroenterol. 2012. PubMed link
• On early detection of bowel cancer: Kuipers EJ, et al. "Colorectal cancer." Nat Rev Dis Primers. 2015. PubMed link
• The importance of colonoscopy as screening: Brenner H, et al. "Colorectal cancer." Lancet. 2014. PubMed link

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See also

Inflammatory bowel disease

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See also

Diverticula