7 Things That Raise Risks of Blood Clots and DVT

If you develop deep vein thrombosis (DVT), a blood clot in the vein deep in the body, it can be serious. Clots that break away and travel from the lower leg or thigh, where they most often form, can become lethal if they lodge in your lungs.

Less clear is what causes deep vein thrombosis in the first place. Numerous medical conditions are thought to cause DVT, but the reason for their link is often unknown. “Almost any disease raises your risk of having DVT, especially while you’re in the hospital, probably through lots of different pathways,” said Elliott Haut, MD, a professor and vice chair in the department of surgery at Johns Hopkins Medicine in Baltimore.

Read on to find out which health conditions may increase risk of DVT.

1. Cancer and DVT Risk

Research indicates that cancer may be one of the health conditions that cause DVT. A review of data compiled by a regional cancer center in the United States over a seven-year period showed that more than 16 percent of 1,874 cancer patients developed a thrombosis, nearly all of them after their cancer diagnosis. “We just know from these large databases that ... having cancer raises the risk,” says Dr. Haut. Also, because cancer patients are often older and not very active, it’s considered likely that age and lack of physical activity contribute to the increased risk for blood clots in cancer patients.

2. Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a term used to describe conditions, such as Crohn’s disease and ulcerative colitis, that are characterized by inflammation in the gastrointestinal tract. And people with IBD are 2 to 3 times more likely to develop serious blood clots (like DVT) than those who do not have IBD, according to research. While experts know that inflammation is one of the risk factors for DVT, Haut says the exact mechanism is not clear. Inflammation affects blood vessels, he says, but there’s less agreement and understanding among the experts on the exact connection between inflammation and DVT.

3. Inherited Clotting Disorders

Blood clotting disorders, such as sickle cell disease, are common causes of deep vein thrombosis because they cause the blood to thicken, stick, and clot more easily. In sickle cell disease, for instance, the irregular shape of the blood cells allows them to stick together more easily and form clots. According to a report from the U.S. Surgeon General, up to 20 percent of all people with DVT have a gene mutation for clotting (known as Factor V Leiden) in which the gene that helps the blood clot normally is abnormal. In addition, 35 percent have at least one genetic risk factor that makes them more susceptible to DVT. The report also notes that people with genetic deficiencies in natural anticoagulants (antithrombin, protein C, and protein S) are much more likely to develop DVT.

4. Heart Disease and Blood Clots

Heart disease, including the blood vessel disease atherosclerosis, commonly called hardening of the arteries, affects the blood vessels in many ways, including increasing the risk for blood clots, notes the American Heart Association (AHA). That makes it one of the health conditions that may cause arterial thrombosis. When you have heart disease, “You have plaque in your blood vessels, and that raises your risk of having a clot there,” explains Haut. “Plaque has a nice smooth lining, and if it cracks, you can have a clot that forms on the crack. That’s the clot that forms and causes a stroke or heart attack.”

5. Infections and DVT Risk

Having a serious infection is another common yet mysterious risk factor for blood clots and DVT. A study in the Journal of Internal Medicine found that people who had a staphylococcus bacterial infection were 3 times more likely than those in the control group to develop DVT. The risk was greatest within a month of their illness. The study suggested that some risk factors are common between the two conditions. Researchers noted that people with a serious infection and other known risk factors for an embolism may benefit from medications to help prevent DVT.

6. Autoimmune Disease

Autoimmune diseases, in which the body’s immune system begins attacking part of the body itself, are among the conditions thought to cause DVT. One study that reviewed data on 200 people with the autoimmune disease lupus found that 23 of the lupus patients experienced 25 instances of blood clotting — a risk rate significantly above the general population. And the Johns Hopkins Lupus Center notes that about 50 percent of people with Lupus have a type of antibody known as antiphospholipid antibodies, which increase the risk of blood clotting. Over a 20-year period, about half the people with Lupus who have these antibodies go on to develop a blood clot, according to Johns Hopkins. People with lupus are also at an increased risk for heart disease, which affects the health of the blood vessels and increases the risk for DVT, per the AHA.

7. Lung Disease and DVT Risk

Lung diseases, especially those that affect the heart, can also increase DVT risk, Haut says. That includes chronic obstructive pulmonary disease (COPD), which can cause heart failure because of the increased workload on the heart from poor lung function. One study from 2021, which looked at 740 COPD patients who had been hospitalized for severe symptoms, found that nearly 6 percent of them had a pulmonary embolism — here again, a rate significantly above the general population or even those in hospital care. Because of this link, a follow-up article from the American College of Cardiology, citing this study, suggested routine monitoring for pulmonary embolism (including imaging) for any COPD patients who are hospitalized for worsening symptoms.