At a glance
Finding blood in your stool is alarming regardless of the amount or colour. The colour of the blood — bright red, dark red, or black — provides initial information about where in the digestive tract the bleeding may be coming from.
This guide covers what different colours typically indicate, what other features to note, and when to seek medical attention. It is not a substitute for clinical assessment — any rectal bleeding should be discussed with a clinician.
Bright red blood
What it typically suggests
Bright red blood indicates a source near the anus or lower rectum. The blood is fresh — it has not been exposed to digestive enzymes or had time to darken.
Common causes
- Hemorrhoids — the most common cause of bright red rectal bleeding
- Anal fissure — bright red blood associated with sharp pain during bowel movements
- Rectal polyps — benign growths that can bleed
- Proctitis — inflammation of the rectal lining
Where people typically notice it
- On toilet paper after wiping
- On the surface of the stool (not mixed through)
- Dripping into the toilet bowl
- Sometimes on underwear
What to do
Small amounts of bright red blood, particularly if associated with a known condition like hemorrhoids, can be discussed with your GP at a routine appointment. If the bleeding is new, persistent, increasing, or accompanied by other symptoms, earlier assessment is appropriate.
Dark red or maroon blood
What it typically suggests
Dark red or maroon blood indicates a source higher in the colon. The blood has spent more time in the bowel, allowing partial digestion to darken it.
Possible causes
- Diverticular bleeding — from outpouchings in the colon wall
- Colonic polyps — larger or higher polyps
- Inflammatory bowel disease — Crohn’s disease or ulcerative colitis
- Angiodysplasia — abnormal blood vessels in the colon wall
- Other colonic sources
Where people typically notice it
- Mixed through the stool rather than on the surface
- In the toilet bowl, sometimes in significant quantities
- May be accompanied by clots
What to do
Dark red or maroon blood generally warrants prompt clinical assessment. Contact your GP for an urgent appointment, or seek emergency care if the bleeding is heavy or you feel unwell.
Black, tarry stool (melaena)
What it typically suggests
Black, tarry, sticky stool with a distinctive strong odour indicates bleeding from the upper digestive tract — the stomach or upper intestine. The blood has been fully digested by stomach acid and enzymes, turning it black.
Possible causes
- Stomach ulcer — one of the most common causes
- Gastritis — inflammation of the stomach lining
- Oesophageal varices — enlarged veins in the oesophagus
- Upper GI bleeding from other sources
Important distinction
Black stool is not always melaena. Other causes of dark or black stool include:
- Iron supplements — commonly cause dark or black stool
- Bismuth-containing medications (e.g., Pepto-Bismol)
- Certain foods — liquorice, blueberries in large quantities
- Charcoal supplements
True melaena is tarry, sticky, and has a distinctive strong, unpleasant smell that is different from the normal variation caused by food or supplements.
What to do
If you suspect melaena (black, tarry, sticky stool not explained by medication or diet), seek urgent medical attention. This may require emergency assessment and potentially hospital admission.
What to note when you see blood
When you notice blood in your stool, recording a few details can help your clinician:
- Colour: bright red, dark red, maroon, or black
- Amount: a few spots, streaks, dripping, or large quantities
- Location: on the paper, on the stool surface, mixed through, or in the bowl
- Pattern: one episode or recurring; how long it has been happening
- Associated symptoms: pain, change in bowel habit, weight loss, fatigue, fever
- What you have been eating or taking: iron supplements, specific foods, medications
The reassurance and the caution
Most rectal bleeding — particularly bright red blood in small amounts — is caused by benign conditions. This is especially true in younger adults without other symptoms or family history.
However, colour alone cannot determine the cause. The same type of bleeding can have different sources in different people. Clinical assessment provides certainty, and certainty — whether the answer is hemorrhoids or something else — is always better than ongoing worry.
The consistent advice: if you see blood in your stool, note what you observe and discuss it with your clinician. Getting checked is not overreacting. It is sensible.