About this symptom
Blood in the stool means blood from the digestive tract has come out with the stool. It may look bright red on the toilet paper, on the stool or in the toilet water; dark red and mixed through the stool; or black and sticky like tar.
The colour is a clue to the source. Black, tarry stool usually means bleeding high up, in the food pipe, stomach or first part of the gut, because digestion darkens the blood on its way through. Red blood usually comes from the lower bowel, rectum or anus. Many causes are minor, such as piles or a small tear, but the same sign can come from an ulcer, an infection, inflammation or cancer, so a doctor should check any blood.
Some foods and tablets change the colour of stool without blood: beetroot, tomatoes and red colouring can make it look red, and iron tablets, black liquorice, blueberries and some stomach medicines can make it dark.
Possible causes
This is not a diagnosis. These are the causes doctors think about, with the ones that are most urgent to rule out first.
- Stomach ulcerBlack, sticky, very smelly stools with burning pain in the upper tummy. Ulcers are the most common cause of sudden bleeding high in the gut. Vomiting blood is an emergency.Read about it
- CirrhosisScarring of the liver can swell the veins in the food pipe and stomach, and they can bleed, causing black stools or vomiting blood. An emergency.Read about it
- Bowel cancerBlood in the stool, red or black, with a change in bowel habit, tummy pain or a lump, weight loss or tiredness. Blood does not mean cancer, but it needs checking.
- Inflammatory bowel diseaseBloody diarrhoea with tummy cramps, pain and bloating, as in ulcerative colitis or Crohn's disease.
- Blood thinners and aspirinBright red blood without pain, or dark stools, if you take blood thinners such as warfarin, or aspirin. Tell your doctor, and do not stop them on your own.
- Stomach bug (gastroenteritis)Bloody diarrhoea with clear slime and feeling and being sick.
- PilesBright red blood after you poo, with or without pain around the bottom, itching or lumps.Read about it
- Anal fissureBright red blood with sharp pain when pooing, often after constipation. It is a small tear in the skin of the anus.
When to get help
See a doctor soon if you have:
- Dark red or maroon blood mixed through the stool, or bloody diarrhoea (see a doctor the same day)
- Any blood on the toilet paper or on the stool, even a small amount of bright red blood
- Stools that have been looser, thinner or harder than usual for 3 weeks
- Blood with weight loss, tiredness, a lump or pain in the tummy
- Blood while taking blood thinners or aspirin
- Blood in a child's stool
If the colour was clearly from food or tablets, there was no blood on the paper, and none of these signs apply, it can wait. See a doctor if you are not sure.
What you can do at home
With any emergency sign, do not stay at home. Otherwise, while you arrange to see a doctor:
Do
- Note the colour, how much blood there was, where you saw it, and how often it happened
- Drink plenty of fluids and eat plenty of fibre to keep stools soft
- Tell the doctor about any blood thinners, aspirin, painkillers or iron tablets you take
Do not
- Do not push hard on the toilet, spend longer there than you need to, or ignore the urge to go
- Do not stop a prescribed medicine, such as a blood thinner, on your own
- Do not decide it is piles without a check
What the doctor will do
The doctor will ask what colour the blood is, how much there was, how long it has been happening, and whether you have pain, a change in bowel habit, weight loss, vomiting or a fever. They will ask about aspirin, blood thinners, painkillers, iron tablets and food. They will examine your tummy and may check the back passage with a gloved finger.
Tests depend on the likely source. They may include:
- Blood tests, including a blood count to see how much blood has been lost
- A stool sample to look for infection
- An (a thin camera passed down the throat to look at the food pipe and stomach) or a (a thin camera passed through the back passage to look at the bowel)
- Scans, if the bleeding is heavy or the source is hard to find
Heavy bleeding may need fluids through a drip or a blood transfusion.
Myths and facts
Things people often say about this. Open each one to see what is true.
Myth“It is only piles, so I can treat it myself.”What is true?
Fact
Piles are a common cause of bright red blood, but you cannot tell the cause by looking. An ulcer, an infection, bowel disease, polyps or cancer can also bleed. Get it checked rather than treating it yourself.
Myth“Black stool is always from iron tablets or something I ate.”What is true?
Fact
Iron tablets, black liquorice, blueberries and some stomach medicines can darken stool. But black, sticky, tarry stool can be digested blood from the stomach or gut, and is an emergency. Do not assume it is the food.
Myth“The bleeding stopped, so there is nothing to worry about.”What is true?
Fact
A single small bleed after a hard stool often goes away without treatment. But bleeding that comes back, goes on for weeks or comes with other changes needs checking, because bowel cancer is easier to treat when it is found early.
Questions to ask your doctor
Tick the ones you want answered and take them with you.
Common questions
When is blood in the stool an emergency?
Get emergency care if you are bleeding non-stop, pass a lot of blood or large clots, have black, sticky stools, vomit blood, or feel dizzy or faint with the bleeding. Do not drive yourself: call for an ambulance or ask someone to take you.
Is bright red blood always piles?
No. Piles and small tears are common causes of bright red blood, but bowel disease, polyps and cancer can cause it too. A doctor needs to check, especially if it keeps coming back or you have other changes in your bowel habit.
Can food or medicines make stool look bloody?
Yes. Beetroot, tomatoes and red colouring can make stool look red, and iron tablets, black liquorice, blueberries and some stomach medicines can make it dark. If the stool is black and sticky, or you are unsure, get it checked.
Does blood in the stool mean cancer?
Not necessarily. Having the symptom does not mean you have bowel cancer, and it has many other causes. But it can be a sign of cancer, which is easier to treat when found early, so a doctor should look into it.
