What Causes Blood Clots in Stools?

Gastrointestinal bleeding, or GI bleeding, can be a common symptom of many different medical conditions. GI bleeding can occur anywhere along the GI tract.

Upper GI bleeding, which can occur anywhere from the mouth to the small intestine, occurs in 100–200 per 100,000 people annually (about 330,000–660,000 people every year). Lower GI bleeding, which includes the small intestine to the anus, occurs in 20.5–27 per 100,000 people annually (about 68,000–89,000 people every year).

It is estimated that 80%–85% of GI bleeding resolves spontaneously, and most causes of GI bleeding can be identified and treated. This article will focus on lower GI bleeding, its causes, symptoms, and when you should seek medical attention.

Anatomical depiction of the gastrointestinal tract

Jeniffer Fontan / Getty Images

Related Symptoms

Depending on the location of the GI bleeding, related symptoms might include:

  • Hematemesis: Bright-red blood in vomit
  • Hematochezia: Bright-red blood in stools, typically indicative of lower GI bleeding
  • Melena: Dark, tarry stools containing blood, usually from the upper GI tract
  • Bright red blood mixed with stool
  • Weakness
  • Abdominal cramps

What Causes Blood Clots in Stool?

There are several medical conditions that can cause blood clots in the stool. Although many conditions will resolve on their own, it is important to be assessed by a healthcare professional skilled in GI tract conditions, such as a gastroenterologist. Causes can include:

  • Hemorrhoids: These are swollen and inflamed veins in the anus and lower rectum. Hemorrhoids can result from straining during bowel movements because of constipation or from lifting heavy objects.
  • Anal fissures: These are small tears inside the anus. They are often caused by straining during bowel movements due to constipation. Blood from anal fissures can appear in the stool.
  • Diverticular disease: This is a medical condition that occurs when small pouches, or sacs, form in the colon and push outward through weak spots in the colon's wall. Diverticulosis can cause inflammation within the large intestine and blood and clots in the stool.
  • Colon cancer: This is a disease in which abnormal cells in the colon or rectum grow out of control. Colon cancer tends to have a genetic component, so having a family member with a history of colon cancer does increase your risk. Colon cancer should start at age 45, and younger for people at high risk.
  • Inflammatory bowel disease (IBD): This includes Crohn's disease and ulcerative colitis, conditions that cause chronic inflammation in the GI tract.

Types of IBD

The two main IBD conditions are:

  • Crohn's disease: Crohn's disease causes chronic inflammation anywhere along the GI tract, from the mouth to the anus. Chronic inflammation can appear in patches scattered throughout the GI tract, damaging several layers of the GI tract.
  • Ulcerative colitis: Ulcerative colitis typically occurs in the large intestine and rectum. Chronic inflammation occurs and typically damages the innermost layer of the large intestine.

Diagnosis and Treatment

Any symptoms of blood clots in the stool should be evaluated by a healthcare provider, such as a primary care physician or a gastroenterologist. Typically, a provider will obtain a thorough health history and perform a physical examination. Depending on your health history and physical exam results, other testing may be considered, such as:

  • Stool testing: Having your stool examined by laboratory professionals can assist your healthcare provider in determining how much blood you are expelling. This is especially helpful if there is blood that is not outrightly visible.
  • Blood testing: Testing of an affected individual's blood can help determine the extent of blood loss.
  • Colonoscopy: This is a test in which a specialized healthcare professional (often a gastroenterologist) uses a flexible lighted scope to inspect the GI tract from the rectum through the large intestine and into the small intestine. They can also take small samples of the intestine, which can be sent to a pathologist to determine what is causing the blood clots.
  • Abdominal computed tomography (CT): This is a diagnostic imaging examination used to obtain images of the GI tract. These images can help your healthcare provider determine any abnormalities that may indicate the cause of blood clots in the stool.

When to Seek Medical Attention

Although many GI bleeding conditions do not result in large loss of blood, it is possible to lose blood quickly. If you have blood clots in the stool along with any of the following symptoms, seek emergency medical treatment:

  • A sudden drop in blood pressure
  • An elevated heart rate without any increased activity
  • Unconsciousness
  • Any other symptoms that seem unusual, such as dizziness or fainting


GI bleeding is a common symptom of many different medical conditions, including hemorrhoids, anal fissures, diverticular disease, Crohn's disease, ulcerative colitis, and more. Always tell your healthcare provider if you are experiencing new or unexplained blood in your stool. They may do blood tests, stool tests, a colonoscopy, and/or a CT scan to determine if it is a medical emergency. Treatments vary depending on the cause.

A Word From Verywell

Blood clots in the stool can be unexpected and worrisome. The good news is many causes of GI bleeding spontaneously resolve and are readily treatable. It is important to report blood in the stool to your healthcare professional as quickly as possible. This will ensure that you are treated quickly and that any serious concerns can be addressed, if needed.

Frequently Asked Questions

  • Can stress cause bloody stools?

    Stress has been linked to increasing irritable bowel disease episodes which can then cause blood in the stool. If you have a chronic disease like Crohn's, learning different tools and techniques to manage stress can help lessen episodes.

  • Can dehydration lead to blood in stool?

    The body needs water to help pass stool. A lack of water can cause stool to harden, which can lead to constipation. Constipation can cause blood in the stool by creating anal fissures.

  • Does IBS cause rectal bleeding?

    Irritable bowel syndrome (IBS) is a group of symptoms that occur together and can cause diarrhea or constipation. While IBS itself does not tend to cause blood in the stool, blood can result if someone with IBS is constipated.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Wells ML, Hansel SL, Bruining DH, et al. CT for evaluation of acute gastrointestinal bleedingRadioGraphics. 2018;38(4):1089-1107. doi: 10.1148/rg.2018170138

  2. National Institute of Diabetes and Digestive and Kidney Diseases. Diverticular disease.

  3. National Institute of Diabetes and Digestive and Kidney Diseases. Symptoms & causes of GI bleeding.

  4. National Institute of Diabetes and Digestive and Kidney Disease. Definition & facts of hemorrhoids.

  5. Centers for Disease Control. What is colorectal cancer?.

  6. Center for Disease Control. What is inflammatory bowel disease.

  7. Ho SM, Lewis JD, Mayer EA, et al. Challenges in IBD research: Environmental triggersInflamm Bowel Dis. 2019;25(Suppl 2):S13-S23. doi:10.1093/ibd/izz076

  8. National Institute of Diabetes and Digestive and Kidney Diseases. Constipation. Updated May 2018.

  9. National Institute of Diabetes and Digestive and Kidney Diseases. Irritable bowel syndrome.

By Pamela Assid, DNP, RN
Pamela Assid, DNP, RN, is a board-certified nursing specialist with over 25 years of expertise in emergency, pediatric, and leadership roles.