Why You Might See Blood in Your Stool

Causes of Bloody Stools and Rectal Bleeding

Like finding a lump in your breast, seeing blood in your stool can send you into a tailspin of panic. For most people, the fear is that this is a sign of colon cancer. Although blood in the stool is considered a red-flag digestive symptom, it doesn't automatically mean that you have a life-threatening illness. Let's take a look at what this scary symptom might actually mean.

When to Call Your Doctor

If you find any blood in your stool or on your toilet paper or see any other evidence of rectal bleeding, the first thing you must do is to call your doctor and set up an appointment. Your doctor will evaluate your symptoms and decide whether or not further investigation is necessary. While it will usually be due to a minor or benign cause, it still needs to be checked so a serious cause can be addressed.


Your doctor can determine the likely cause and what treatment is appropriate. These are some of the possibilities.

Common Causes

Common causes of bloody stools
Verywell / JR Bee

Hemorrhoids: One of the most common causes of blood in the stool is that it is the result of hemorrhoid that has started to bleed. Hemorrhoids appear when blood vessels in the rectum or anus become swollen and inflamed. Bleeding from a hemorrhoid is typically bright red in color.

Anal fissures: Anal fissures are another possible cause of blood in the stool. An anal fissure is a tear in the tissue lining your anus. In addition to causing bright red blood to appear in your stool, anal fissures may also cause symptoms of anal pain and/or itching, as well as pain during bowel movements.

Less Common Causes

Colon polyps: Colon polyps are growths in the colon that are at risk for developing into cancerous tumors. Typically polyps do not cause any symptoms, but bleeding can occur and show up on or in your stool.

Inflammatory bowel disease (IBD): Both of the two forms of IBD, ulcerative colitis, and Crohn's disease, can cause blood to appear in your stool.

Diverticular bleeding: Diverticular disease is when small pouches exist along the lining of your large intestine. Although it is not terribly common, these pouches can bleed. If this happens, you may see a large amount of blood in your stool. Most often, this bleeding will stop suddenly. However, in a small number of cases, the condition can become life-threatening and require admission to an intensive care unit. If you experience large amounts of blood on your stool, seek medical help immediately.

Colon cancer: Blood on or in the stool is often the first noticeable sign of present colon cancer. This is why it is essential that any sign of blood on the stool be brought to your doctor's attention. Blood from a cancerous growth in the colon may cause the stool to appear dark, black, or tar-colored.

Bleeding from the esophagus, stomach or small intestine: Disease occurring higher up in the digestive tract can also cause the stool to appear dark red or black. Possible culprits include peptic ulcers, esophagitis, esophageal tears, and tumors.

Benign Changes in Stool Color

Sometimes stool color can change due to eating certain foods or taking certain supplements. You might confuse this with blood in the stools. Here are some examples:

  • Pepto Bismol
  • Iron supplements
  • Foods with black or red food coloring
  • Beets and other red vegetables

Diagnostic Tests

Based on your symptom picture, your doctor will choose which diagnostic tests are most appropriate. Most doctors will take a thorough history and do a physical examination, which may include a rectal exam. Blood work may or may not be taken. Some other possibilities include:

A Word From Verywell

Do not ignore any signs of blood in your stool. While you don't need to overreact, the proper action is to immediately bring your symptoms and concerns to the attention of your doctor. With a proper diagnosis, the underlying problem can be appropriately addressed.

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Article Sources
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  1. Penner RM, Majumdar SR. Patient education: Blood in the stool (rectal bleeding) in adults (Beyond the Basics). UpToDate. Literature review current through December, 2019.

  2. Cleveland Clinic. Rectal bleeding: possible causes. Reviewed January 27, 2015.

  3. Centers for Disease Control and Prevention. What is inflammatory bowel disease (IBD)? Reviewed March 22, 2018.

  4. HealthLinkBC. Diverticular bleeding. November 7, 2018.

  5. American Society for Gastrointestical Endocscopy. What is colorectal cancer?