Why Blood Clots Are More Common in People With IBD

Illustration of a blocked artery - stock illustration


It’s well known that inflammatory bowel disease (IBD) is associated with what's called extra-intestinal manifestations: conditions that are related to IBD but aren’t found in the digestive tract. One of these is the risk of developing blood clots.

The increased risk of blood clots in people with Crohn's disease and ulcerative colitis is known to IBD experts but it may not be as well understood by other physicians and by people who have IBD. It's unclear exactly why people with IBD are at risk for blood clots but it's thought to have to do with disease activity and changes in the blood that promote clotting. 

While the risk of blood clots has been shown to be higher in people with IBD, there are things that can be done to prevent them. What’s vital is that people with IBD understand their personal risk of blood clots and that physicians take steps to avoid this complication when necessary, such as after surgery. People with IBD can also familiarize themselves with symptoms of a blood clot, such as pain, swelling, tingling, and pale skin in one leg. The overall risk of blood clots in people with IBD who don’t have other risk factors is still considered low.

What Are Blood Clots?

Blood normally clots in order to stop bleeding, such as when there is a cut or a wound. However, when the blood clots too easily or forms large clots, the blood flow through a vein or an artery may be blocked. When clots travel through the circulatory system and wind up at an organ such as the heart, brain, kidneys, or lungs, it can cause damage to those organs or complications such as a heart attack or a stroke.

Who Is at Risk?

Each year, it’s estimated that 900,000 people in the United States experience a blood clot and between 60,000 and 100,000 will die from this complication. People could be at risk for blood clots based on a number of factors. Some of the conditions that are associated with blood clots include atherosclerosis, atrial fibrillation, deep vein thrombosis (DVT), diabetes, heart failure, metabolic syndrome, peripheral artery disease, and vasculitis. There are also several independent risk factors for blood clots, which include:

  • Being on bed rest
  • Cancer diagnosis
  • Current hospitalization
  • Dehydration
  • Family history of blood clots
  • Injury to a vein
  • Obesity and overweight
  • Personal history of blood clots
  • Personal history of miscarriages
  • Recent surgery
  • Recent accident (such as a car accident)
  • Sitting for long periods
  • Smoking
  • Use of medications that contain estrogen (such as birth control or hormone therapy)

The Evidence of Blood Clot Risk in IBD

One study on blood clots was done on almost 50,000 adults and children with IBD in Denmark between 1980 and 2007. What the researchers concluded was that when compared to people without IBD, people with IBD had twice the risk of pulmonary embolism and deep vein thrombosis.

Even after correcting the data for other potential causes for blood clots, such as heart disease, diabetes, congestive heart failure, and the use of certain medications, the risk was still 80 percent higher in the IBD group.

Another study published in 2004 looked at 618 people with IBD as well as people with rheumatoid arthritis and celiac disease and compared them to a control group. As is often done in such studies, each person with IBD was matched to a person in the control group who has the same age and gender. After looking at the data on blood clots, the researchers found that people with IBD experienced blood clots at a rate of 6.2 percent (which was 38 patients), compared to 1.6 percent in the group that did not have IBD.

A 2010 study done in the UK looked at the risk of blood clots in patients with IBD who were not hospitalized and did not have active disease as well as those who were experiencing a flare-up and those who were in the hospital. There were 13,756 patients with IBD included and the results showed that even when not in a flare-up people with IBD had a risk of a blood clot that was three times greater than that of the control group. People who were hospitalized for their IBD had a risk of blood clots that was three times more than other patients in the hospital. A flare-up of IBD was associated with a risk of blood clots that was eight times that of people in the control group that did not have IBD.

What All the Data Means

The numbers from the research can sound scary but there are a number of factors to take into consideration. A person’s risk of blood clots is going to be based on several factors and having IBD is now understood to be only one of these.

Gastroenterologists should be aware of this increased risk and can help put one’s personal risk into perspective, taking into account other risks such as age, family history, activity level, medications, and pregnancy. Guidelines from the Canadian Association of Gastroenterology published in 2014 recommend that anticoagulant medications (which may prevent blood clots) be used in certain patients who have IBD, particularly while hospitalized, after surgery, and if a blood clot has already occurred. It’s not recommended that people with IBD receive medications to prevent blood clots on a routine basis.

Reducing the Risk

Lowering the risk of blood clots includes advice such as getting exercise, keeping to a healthy weight, drinking enough water, and managing related conditions such as diabetes and heart disease.

For people with IBD who are in the hospital, anti-clotting medications, which reduce the risk of blood clots, might be prescribed. There has been some discussion among experts about offering anticlotting medications to people with IBD who are not hospitalized but so far doing this is not thought to offer much in the way of benefit.

Every person with IBD will need to understand their personal risk of blood clots and work with a physician to know when it might be necessary to use medication to prevent them.

A Word From Verywell

Gastroenterologists may be aware of the blood clot risk but other physicians may not. This highlights the need for everyone on the IBD care team to communicate and put risk factors into perspective. This also means that when people with IBD experience a blood clot risk factor, such as having surgery or being in the hospital, it’s important that the doctors take the potential for a higher blood clot risk into account.

People with IBD who have concerns about their personal risk of a blood clot because of risk factors or family history should talk with a gastroenterologist about preventing blood clots.

Was this page helpful?

Article Sources

  • Division of Blood Disorders National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention "Venous Thromboembolism (Blood Clots): Data & Statistics.” CDC.gov. 6 Apr 2017.
  • Grainge MJ, West J, Card TR. "Venous thromboembolism during active disease and remission in inflammatory bowel disease: a cohort study.” Lancet. 2010;375:657-63. doi: 10.1016/S0140-6736(09)61963-2
  • Kappelman MD, Horvath-Puho E, Sandler RS, et al "Thromboembolic risk among Danish children and adults with inflammatory bowel diseases: a population-based nationwide study.” Gut. Published Online First: 21 February 2011. doi:10.1136/gut.2010.228585
  • Miehsler W, Reinisch W, Valic E, et al. "Is inflammatory bowel disease an independent and disease specific risk factor for thromboembolism?" Gut. 2004;53:542-548. doi: 10.1136/gut.2003.025411
  • Nguyen GC, Bernstein CN, Bitton A, et al. "Consensus Statements on the Risk, Prevention, and Treatment of Venous Thromboembolism in Inflammatory Bowel Disease: Canadian Association of Gastroenterology.” Gastroenterology. 2014;146:835–848. doi: 10.1053/j.gastro.2014.01.042