Blood in the Stool: What Does It Mean?

An illustration showing colon cancer.
An illustration showing colon cancer. BSIP/UIG/Getty Images

If you see blood in stools, technically referred to as hematochezia, you may want to ignore it and hope for the best. This is a common reaction, but it won't help you get to the bottom of what's causing the symptom. Blood in the stools can be bright red or dark, black, and/or "tarry" looking, and it always requires your doctor's attention, although in many cases it will have a benign cause.

Though colon cancer isn't to blame in all cases (the cause could be something less serious), blood in stools can be a signal of the disease.

So, you should make it a priority to schedule an appointment. If colon cancer is diagnosed in the earliest stages, survival rates are well over 90 percent. If the cancer is more advanced and has spread beyond the colon, survival rates drop dramatically. The sooner you get a diagnosis the better.

What's Causing There to Be Blood in My Stools?

Generally, blood in the stool means that there is bleeding somewhere in the large intestine. The color of the blood can be an indication of where the bleeding is occurring. If the blood is bright red and "fresh" looking, the bleeding is likely occurring toward the end of the colon or in the rectum. If bleeding is occurring higher up in the colon, the blood will be dark brownish to black, referred to as tarry stools. Sometimes, the blood may not even be visible on the stool, and this is termed occult gastrointestinal bleeding.

By far, the most common causes of visible blood in the stools are diverticulitis and hemorrhoids.

Other conditions and situations that can cause blood in the stools include:

  • recent trauma; for example, blood in the stools can occur after a colonoscopy or flexible sigmoidoscopy examination (only lasts a day or two; is not serious)
  • lack of blood flow to the intestines, resulting in bowel ischemia
  • use of non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin and ibuprofen

Sometimes the stools may appear darker than normal, leading people to believe they have blood in their stools, even when blood is not present. Consuming iron supplements, blueberries, beets, blackberries, and other blue, red, purple, and black foods can cause this to occur.

See your doctor if you notice blood in your stool or changes in the color, consistency, or frequency of your bowel movements. Easily treatable conditions such as hemorrhoids may be the cause, but it is better to err on the side of caution and get the correct diagnosis. If there's any reason to suspect cancer, the quicker you get to the bottom of your symptoms, the better (no pun intended).


American Cancer Society. Blood in Stool. Accessed: July 22, 2009.

Medline Plus. Medical Encyclopedia. Bloody or Tarry Stools. Accessed: July 22, 2009.

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