Common Causes
It is important to know your risk factors and talk with your healthcare provider about what, if anything, you can do to lower your risk of a dangerous clot. Blood clots primarily occur in the veins and arteries, interrupting blood flow and potentially leading to heart attacks and strokes.
Atherosclerosis
When fatty deposits, called plaques, develop in the linings of the arteries (often due to high cholesterol), it is known as atherosclerosis. If a plaque ruptures in a coronary artery, it will cause a blood clot to form, potentially causing permanent damage to the heart muscle, or, worse, a heart attack.
Atrial Fibrillation
Atrial Fibrillation (AFib) is the most common form of heart arrhythmia, causing your heart to beat too quickly or skip beats, interrupting blood flow. When this happens, blood can pool in the heart and form clots, which can ultimately travel to the brain and lead to a stroke.
Diabetes
Diabetes produces changes in your blood that make it more prone to clotting.
Prolonged Immobility
Sitting or lying down for long periods—due to prolonged bed rest after illness or a long airplane flight, for example—can cause blood to pool in the legs, leading to deep vein thrombosis (DVT) and, worst-case scenario, pulmonary embolism if the clot travels to the lungs.
Getting up, walking around, and stretching can help you avoid DVT.
Surgery
A blood clot is more likely to form during or after surgery; one reason for this is prolonged periods of inactivity due to lying on an operating table and staying in bed while recovering.
The type of surgery you have performed can also increase the risk of blood clots after the procedure. Clots are more common after major surgeries, particularly those involving the pelvis, abdomen, knee and hip.
A surgery where your heart is stopped, typically a heart bypass surgery (CABG), also ups this risk.
Cancer and Cancer Treatments
Cancer itself, as well as certain chemotherapy drugs, can increase the blood’s clotting ability. Cancer patients are also likely to have long periods of inactivity, such as during chemotherapy treatments or while on bed rest.
If you are undergoing treatment for cancer, it’s important to be aware of the symptoms of a blood clot.
Genetics
Though they are relatively rare, there are some inherited blood clotting disorders that can make you more prone to developing clots compared to the general population.
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Factor V Leiden: In factor V Leiden, a substance known as factor V, which is important to the clotting process, can get out of control, causing a benign clot to become dangerous. Between 3 percent and 8 percent of people with European ancestry carry the gene mutation associated with the disorder.
Prothrombin gene mutation: Patients with this disorder have a genetic defect that results in an overabundance of prothrombin, a blood clotting protein. About 2 percent of whites in the United States and Europe have a form of this mutation.
Antithrombin, protein C, and protein S deficiencies: Patients with these rare mutations have a reduced amount of natural anticoagulants in their blood and are thus more prone to clotting.
You’re more likely to have a genetic cause of excessive blood clotting if you have family members who have had dangerous blood clots, a personal history of repeated blood clots before the age of 40, and/or a personal history of unexplained miscarriages.
Lifestyle Risk Factors
While genetic disorders and certain chronic conditions are not things you can control, the following lifestyle-associated risk factors generally are. Your healthcare provider can help you find ways to modify your behaviors and choices to lower your risk of a blood clot.
Smoking
Over time, smoking can damage the lining of the blood vessels, making clots more likely. If you have another risk factor, such as being pregnant or using birth contorl, your risk is further increased.
Talk to your healthcare provider about a smoking cessation program if you need help quitting cigarettes.
Obesity
Carrying extra fat can slow blood flow and put more pressure on your veins. Being significantly overweight can sometimes coincide with an inactive lifestyle and/or diabetes, both risk factors in and of themselves.
A nutritionist or a group weight-loss program can help you learn how to make healthy food choices and start an exercise program.
Pregnancy and Postpartum
Pregnancy increases the number of platelets and clotting factors in the blood, increasing a woman’s chance of developing a clot. The uterus can also compress the veins slowing blood flow, which can lead to blood clots.
Hormone Replacement Therapy (HRT)
Some forms of HRT, particularly those containing estrogen, can increase blood clot risk. Since HRT comes in many forms—using different combinations of hormones, including progesterone (or its synthetic form, progestin)—it’s important to talk to your healthcare provider about the one that is safest for you.
Birth Control Pills
As with HRT, many pills, patches, and rings contain estrogen, which can increase your risk. Pills containing drospirenone, a form of the hormone progestin, may increase blood clot risk compared to birth control that uses a different progestin.
Yaz, Yasmin, Beyaz, and Safyral are birth control pills that contain drospirenone.
But there is no need to panic if you are currently using a birth control method that contains drospirenone. There are many different formulations, containing different combinations of hormones.
If you have any concerns or questions, discuss the risks and benefits of using any form of birth control pills, especially if you smoke or have other risks factors for blood clots.
Read more about how blood clots are diagnosed.
Skin tenderness, redness, and warmth in the area of the clotSwellingDizzinessNumbness or weaknessChest painShortness of breathNausea or vomitingBreaking out in a cold sweat
