Possible causes of blood in stool include gastroenteritis, anal fissures, hemorrhoids, inflammatory bowel disease, and more. Treatment can depend on the underlying cause.

Below, learn more about the possible causes of bloody stool, including those more common in children. Also, find out how doctors diagnose and treat these issues.

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An injury to the gastrointestinal (GI) tract, inflammation, and ulcers can all cause the lining of the digestive tract to bleed. In some cases, perforation may occur, resulting in bleeding, abdominal pain, and severe illness.

If bleeding occurs in the GI tract, the blood passes out of the body with the stool.

Specific health issues that can lead to bleeding include the following:


Gastroenteritis refers to viral, fungal, or parasitic infections that affect the stomach and intestines.

It can cause:

In rare cases, some types of bacteria can cause bloody diarrhea.

Symptoms of gastroenteritis can last up to 10 days, depending on the cause.

Infection usually results from:

  • consuming food and water from contaminated sources
  • improper hand hygiene
  • contact with people who have an infection
  • consuming spoiled food, resulting in food poisoning

In the past, people often referred to viral gastroenteritis as stomach flu. Doctors no longer use this term as this is a gastrointestinal disease, while flu is a respiratory disease.

What is bacterial gastroenteritis?

Anal fissure

Anal fissures are small tears in the lining of the anus. They may bleed and cause pain during a bowel movement.

Possible causes include:

  • inflammatory bowel disease (IBD)
  • trauma
  • tumors
  • infections
  • having a tight sphincter, the muscle that allows the anus to open and close


Hemorrhoids are swollen veins in the lower rectum. Straining or passing hard stool can rupture these veins, leading to bloody bowel movements.

People with hemorrhoids may notice a few drops of blood on the stool, on tissue, or in the toilet bowl. Factors that increase the risk of hemorrhoids bleeding include:

  • constipation
  • diarrhea
  • sitting or standing for a long time
  • obesity
  • heavy lifting
  • pregnancy

Peptic ulcers

Peptic ulcers are open sores that develop in the lining of the stomach or duodenum.

A peptic ulcer that forms on a blood vessel may cause bleeding and bloody stools.

Other symptoms include:

  • bloating and belching
  • nausea
  • vomiting
  • reduced appetite and weight loss

These ulcers can result from infection with Helicobacter pylori bacteria or from the long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs).


Diverticula are small pockets that can form inside the colon. They are prone to infection and inflammation and can sometimes rupture and bleed.

The medical term for infection and inflammation of diverticula is diverticulitis. Diverticulitis is a type of diverticular disease.

Other symptoms of diverticular disease include:

  • constipation
  • diarrhea
  • abdominal pain
  • bloating

Experts do not know what causes diverticular disease.

Inflammatory bowel disease

Inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis, can cause bloody stool.

As well as rectal bleeding or blood in stool, symptoms include:

  • abdominal pain
  • diarrhea
  • weight loss
  • fatigue

Experts do not know exactly what causes IBD, but it involves changes to the immune system. Genetic factors may also play a role.

Anal fistula

An anal fistula is a small tunnel that forms between the end of the bowel and the skin near the anus. Fistulas can also start in the colon and lead to another organ or the surface of the skin.

Colonic and anal fistulas are rare but can result as a complication of:

After an infection, pus can collect in tissues surrounding the anus. As the pus drains, it leaves behind the fistula, which may continue to ooze pus or blood.

Symptoms include:

  • diarrhea
  • pain
  • weight loss
  • stool or gas passing through the skin, vagina, or urinary tract instead of the anus


A person may experience GI bleeding as a side effect of blood-thinning medications, such as:

Anyone who takes a blood-thinning medication and has a bloody bowel movement should notify their doctor immediately if they see blood in their stool.

Colon polyps

Colon polyps can lead to bloody stools. These small growths may be benign or precancerous.

Often, there are no symptoms, but a person may notice:

  • red streaks in stool
  • black stool
  • bleeding from the rectum
  • blood on underwear or tissue after wiping
  • fatigue due to anemia

Experts do not know why polyps occur, but they become more likely as people get older. A family history of polyps can also increase the chance of having them.


Cancerous tumors of the GI tract can weaken the lining of the GI tissues, causing them to bleed.

However, cancer may be present without any visible signs of bleeding. People with a higher risk of cancer in the digestive system can ask a doctor about screening with a FIT test, also known as a fecal occult blood test.

This can show if small traces of blood are present in stool that are not visible to the eye.

Bloody stool may be especially common in infants. Some causes include:

  • Food allergies: Allergies to proteins in food or milk can cause gastroenteritis that leads to intestinal bleeding.
  • Structural changes: Issues that cause the intestines to become twisted — such as intestinal malrotation and volvulus — may lead to bleeding.
  • Necrotizing enterocolitis: This serious disease causes inflammation and tissue death within the large intestine. It usually affects premature or newborn babies. The disease can cause:
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Blood in stool may result from bleeding in the upper or lower GI tract — and the color of the blood can help indicate its source.

Black, tarry stool

Black, tarry stool may point to a bleed in the upper GI tract. As a general rule, the darker the blood, the higher the source of the bleed.

The upper GI tract includes the mouth, esophagus, stomach, and upper part of the small intestine, called the duodenum.

According to the American College of Surgeons, upper GI bleeding is more common than lower GI bleeding, accounting for about 70% of all GI bleeds.

Bright red blood

This is usually a sign of a bleed in the lower GI tract. This section consists of the large intestine, rectum, and anus.

No change in color

Sometimes there is blood in stool, but it only shows up in a lab test. It is not visible in the stool. For people with a family history of bowel cancer, a doctor may recommend screening.

A doctor will likely ask:

  • how much blood was visible
  • whether it was only on the toilet paper or in the bowel movement
  • how often the blood appeared
  • if there was any pain or other symptoms associated with the bowel movement

They may carry out an examination of the rectum and order tests to help identify the cause and check how much blood the person has lost.

The next steps depend on how much blood was lost.

Emergency situations

If a person reports significant blood loss, a doctor may order a CT scan to rule out perforation.

If there is no perforation, they may perform an urgent endoscopy.

This involves inserting a thin, flexible tube with a camera at one end into the upper or lower end of the GI tract, depending on the type of blood the person has seen. In this way, they will look for the source of the bleeding.

An upper endoscopy involves guiding the endoscope through the mouth and down into the upper GI tract. A colonoscopy is a form of endoscopy that involves inserting the endoscope into the anus and through the lower GI tract.

Once the doctor has identified the source of the bleeding, they can insert tiny instruments through the endoscope and use them to repair the damaged tissue.

If the doctor is unable to resolve the bleed, they may recommend surgical removal of all or part of the damaged area.

Nonemergency situations

If the bleeding does not appear to be life threatening, the doctor may order or perform a:

  • Fecal immunochemical blood test (FIT): Also known as a fecal occult blood test, this involves analyzing a stool sample for the presence of blood that may not be visible to the eye.
  • Complete blood count: This blood test can help determine the extent of blood loss.
  • Digital rectal examination: This involves examining the rectum manually, to identify hemorrhoids or other causes of bleeding within the rectum.
  • Endoscopy: This procedure allows the doctor to view the inner lining of the GI tract.

The best approach depends on the cause and source of the bleeding within the GI tract.

If bleeding results from an ulcer, infection, or inflammation, the doctor may prescribe medications.

If cancer is present, they will recommend a suitable course of treatment, depending on the stage and other factors.

In some cases, surgery is necessary to prevent further bleeding. The doctor may perform it using endoscopy or colonoscopy. The procedure may involve:

  • injecting medicines to stop the bleeding
  • cauterizing the site using a heat probe, electric current, or laser
  • closing off the affected blood vessels using a band or clip

A person should seek medical attention as soon as possible if they notice black or dark red stool or have bloody diarrhea.

A person with the following symptoms may be losing a large amount of blood and should seek emergency medical help:

Some symptoms are less severe but still warrant investigation. A person should see a doctor if they experience:

  • unexplained abdominal pain
  • pain when passing stool
  • a small amount of blood in a bowel movement

Here are some answers to questions people often ask about blood in stool.

Is blood in your stools serious?

Often, blood in stool is a sign of hemorrhoids or piles. In some cases, however, it can be a sign of a more serious condition, such as bowel cancer or internal bleeding.

It is always best to check with a doctor if you notice blood in your stool. If you do not have blood in your stool, but there is a family history of bowel cancer, ask about screening.

When should I be worried about blood in my stool?

People should see a doctor as soon as possible if:

  • the stool is black or dark red
  • bloody diarrhea occurs
  • there is a lot of blood, there are blood clots, or bleeding is non-stop

Non-stop bleeding is a medical emergency. A person should call 911 or go to the emergency room.

Blood in the stool may turn out to be nothing alarming but it is always best to discuss it with a healthcare professional. They can help determine whether or not further testing is necessary.

A person should seek emergency medical care if there is a lot of blood, if there are blood clots, or if they have other signs of blood loss, such as dizziness or fainting.