Living with ulcerative colitis (UC) increases the likelihood of developing a blood clot. However, preventive measures may help reduce this risk.

UC is one of the most common forms of inflammatory bowel disease (IBD), but the cause is not well known. Some research has suggested that the immune system mistakenly attacks “good” bacteria in the intestines, leading to intestinal inflammation associated with UC.

This chronic inflammation can increase a person’s risk of developing several other health conditions, including blood clots.

This article examines what researchers have found about the link between UC and blood clots, when blood clots become problematic, ways to lower this risk, and when to speak with a doctor.

Researchers across various studies have identified an increased risk of blood clots in people living with UC, as well as several potential reasons for this heightened risk.

In a 2022 review, researchers identified several studies that found an increased risk of various thromboembolic events in people with IBD. Thromboembolic events are when a blood clot forms in one blood vessel, becomes dislodged, and then travels to another blood vessel, causing a blockage.

The researchers noted that previous studies identified a twofold increase of deep vein thrombosis (DVT), a type of deep blood clot in the leg, pelvis, or occasionally the arm, in people living with UC.

In addition, they reported that people living with IBD seem to have an increased risk of developing blood clots at a younger age. They also noted that people with UC have an increased risk of mortality from a thromboembolic event.

This increased risk of blood clots in UC may be due to various factors.

Inflammation and other shared risk factors

According to 2021 evidence, inflammation can play a role in blood vessel damage, leading to blood clotting in the arteries — a thrombotic event.

A 2017 case study reported similar damage due to inflammation. However, these researchers also noted that the study participant had inadequate management of UC, which may have contributed to the development of blood clots.

UC also contributes to three well-known causes of blood clots, including:

  • reduced blood flow, often occurring due to prolonged bed rest
  • damage to blood vessels, which can occur due to trauma or following surgery
  • increased tendency for blood to clot, which may occur due to inflammation


Other research has explored the idea that certain genetic factors may increase the risk of blood clots in people living with UC.

In a 2020 study, researchers noted that identifying certain genetic markers in people with UC may help identify those at increased risk of blood clots earlier.

They found that genetic testing identified 1 in 7 people living with IBD who have a 2.5 times or higher risk of developing potentially fatal blood clots. They also noted that thromboembolic disease is a leading cause of death in people living with IBD. Therefore, identifying this risk early on can potentially be lifesaving.

Blood clots have several known risk factors beyond living with UC.

The three major risk factors include:

  • pregnancy
  • cancer
  • hospitalization and surgery

However, other factors may also increase a person’s risk of developing blood clots, including:

  • taking estrogen-containing birth control
  • having obesity or overweight
  • smoking
  • sitting for long periods
  • experiencing prolonged immobility
  • taking estrogen-containing hormone replacement therapy
  • experiencing an injury, particularly to a vein
  • having a family or personal history of blood clots

All blood clots can cause issues.

Experts previously considered superficial venous thrombosis — a blood clot that occurs in veins near the surface of the skin — as a benign, self-limiting condition. However, recent findings suggest it is closely associated with the occurrence of DVT and other types of clots in the veins.

DVT often develops in a person’s legs or arms. It can block blood flow, leading to several symptoms, such as pain and swelling in the affected area. Without treatment, the clot can break free and travel to the lungs. This is known as a pulmonary embolism.

Every 6 minutes, one person living in the United States dies from blood clots. Treatment is necessary to prevent complications and potential death.

Several steps can help lower the risk of developing a blood clot, including:

  • learning personal risk factors
  • talking with a doctor about individual risk
  • recognizing the signs and symptoms of a blood clot
  • seeking emergency care if signs or symptoms occur
  • talking with a surgeon before surgery about blood clot risk

Other steps to lower risk include:

  • eating less salt — often listed as sodium
  • wearing loose-fitting clothing
  • staying active throughout the day
  • avoiding standing or sitting for longer than 1 hour at a time
  • shifting or taking breaks to move regularly during long trips
  • wearing compression stockings as recommended
  • raising the bottom of the bed by about 4–6 inches
  • avoiding placing pillows under the knees
  • preventing injury to the legs

A person living with UC can discuss their individual risk for blood clots with a doctor based on their current health and other factors. A doctor may recommend wearing compression stockings or prescribe medications to help prevent clotting.

A person should consult a doctor as soon as possible if they develop any signs or symptoms of a blood clot.

Signs of DVT include:

  • swollen, painful skin that is warm to the touch — people with lighter skin may notice redness
  • swelling of the leg or arm
  • pain or tenderness not caused by an injury

Signs of a pulmonary embolism include:

  • breathing difficulties
  • having a fast or irregular heartbeat
  • coughing up blood
  • experiencing chest pain that worsens with deep breaths

UC and blood clots share various risk factors, from inflammation to genetics. Other outside risk factors, including injury or a sedentary lifestyle, may also make blood clots more likely to occur.

A person living with UC can consider discussing their individual risk of blood clots with a healthcare professional. Taking preventive steps and seeking treatment at the first signs of a clot can help improve outcomes.