What Is Deep Vein Thrombosis?
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Medically reviewed by Christopher Lee, MD
Deep vein thrombosis (DVT) is one of two types of venous thromboembolism, a medical condition characterized by a blood clot (also known as thrombi) forming within a deep vein in the body. These clots block the normal flow of blood back to the heart, which can lead to various complications. Blood clots can occur almost anywhere in the body, but in the case of deep vein thrombosis, they tend to occur in the lower leg or thigh.
Blood clotting, or coagulation, naturally occurs in your body to protect you from excessive bleeding (such as during an injury). In most cases, your body naturally dissolves the blood clot as you heal. However, sometimes the blood clot doesn't dissolve and can be a danger to your health, causing deep vein thrombosis. DVT can also occur without injury or known cause.
Approximately 900,000 people are affected by DVT in the United States each year, with about a third of them experiencing long-term complications. DVT can lead to a medical emergency called pulmonary embolism, which is when a blood clot from one area of the body travels through your bloodstream to the lungs. Pulmonary embolisms usually stem from blood clots in the deep vein of the leg.
DVT Symptoms
Nearly half of people with a DVT don’t experience symptoms. Of those who experience symptoms, the following are the most likely:
Pain or tenderness
Cramping, aching, or increased warmth around the area
Red or discolored skin
Thickening or firmness of the affected vein, which is referred to as a "cord"
Generally, these symptoms occur in the larger veins of the thigh or lower leg, usually on one side of the body.
Related: Deep Vein Thrombosis: I Thought It Was Just a Sprained Ankle
What Causes Deep Vein Thrombosis?
Anyone can develop deep vein thrombosis. Anything that slows your blood flow long enough for a clot to form can cause DVT. One of the most common risk factors is being immobile (not moving) for many hours. Therefore, leading an inactive or sedentary lifestyle is one of the most common causes, among other reasons for immobility, including:
Being confined to bed (e.g., after surgery or a medical condition)
Limited or restricted body movements (e.g., wearing a cast on a leg to help heal a broken bone)
Prolonged sitting, especially with crossed legs
Paralysis (the loss of voluntary muscle movement in an area of the body)
Certain medications and medical conditions that raise the risk of blood clotting can also contribute to the occurrence of DVT, including:
Injury to a vein, which can be caused by fractures or severe muscle injuries
Increased estrogen levels, usually caused by taking birth control pills, undergoing hormone replacement therapy, or pregnancy (and up to 3 months after giving birth)
Heart disease
Lung disease
Cancer and cancer treatments
Inflammatory bowel disease (Crohn's disease or ulcerative colitis)
Risk Factors
Genetic and lifestyle factors that can increase your risk of DVT include:
A person or family history of previous DVT, pulmonary embolism, or a clotting disorder
Age (DVT risk increases with age)
Obesity
Having a catheter placed in a central vein
Women in their childbearing years are at higher risk of developing blood clots than men. The chance is also higher among pregnant people and people who take birth control pills or receive hormone therapy.
Major surgeries, especially of the abdomen, pelvis, hip, or leg regions
Diagnosis
Diagnosing DVT involves a comprehensive evaluation by your healthcare provider. They may refer you to a vascular specialist, which is a doctor who diagnoses and treats problems with your blood vessels and circulation. They will discuss your symptoms with you, review your medical history, conduct a physical examination, and perform a range of imaging or blood tests.
One commonly used test is the D-dimer test. It measures a substance in your blood that is released when a blood clot's fibrin protein (which helps stop bleeding) dissolves. High levels of this substance in the test results could indicate the presence of DVT. In some cases, this test is used as an initial step to detect signs of a blood clot, particularly in individuals who are otherwise healthy.
Compression ultrasound is another diagnostic method. It examines the deep veins in your legs for blood clots. During this test, sound waves are used to create images of blood flow in your veins. The healthcare provider conducting the test may apply pressure to your veins to check if they compress normally or if they feel rigid due to blood clots.
In certain situations where your diagnosis cannot be determined from a compression ultrasound, magnetic resonance venography may be suggested. This specialized imaging technique uses a magnet to map out detailed images of your veins. Before the test, your provider may inject a special dye into your veins using an intravenous tube (IV). This helps ensure your veins are visible during the test.
Treatments for DVT
Most people can treat and manage deep vein thrombosis at home. In cases where DVT is severe or has led to complications, management should be done in a hospital.
Your healthcare provider will likely suggest blood-thinning medications (commonly called blood thinners) as part of your treatment. This will prevent your blood clot(s) from growing larger. It should also reduce your risk of pulmonary embolism. If blood thinners are not an option, then a procedure may be recommended. Severe cases of DVT may require localized thrombolytics, which are medications used to dissolve large blood clots. However, this is relatively uncommon.
A catheter-assisted blood clot removal procedure is sometimes warranted. This procedure uses a flexible catheter tube (which is inserted via a vein) to reach a blood clot. A tool is inserted through the tube to break up the clot.
Elastic compression stockings are tools that are sometimes used in addition to other treatment options. A 2022 study found that wearing elastic compression stockings for 24 months decreased the chances of developing post-thrombotic syndrome in people with DVT who could not have a procedure to remove the clot. Post-thrombotic syndrome is characterized by chronic pain or swelling in the area of the blood clot.
Prevention
The best way to prevent deep vein thrombosis is through regular physical activity. When sitting for extended periods, especially during long trips lasting over four hours, take breaks and walk around every 1 to 2 hours. Additionally, you can exercise your legs while seated by performing the following movements:
Raise and lower your heels while keeping your toes on the floor.
Raise and lower your toes while keeping your heels on the floor.
Tightening and releasing your leg muscles.
Wearing loose-fitting clothes can also help reduce your risk of DVT, as too-tight clothing can reduce your blood circulation.
Related Conditions
DVT can cause inflammation of the affected vein, which is referred to as thrombophlebitis. This can be quite painful, causing warm, red or discolored skin and painful swelling.
The detachment or breaking off of a blood clot can result in a pulmonary embolism. This occurs when the blood clot travels to the lungs and restricts adequate blood flow to your organs. Pulmonary embolism is the most serious complication caused by deep vein thrombosis.
A Quick Review
A DVT is a life-threatening event that can happen to anyone. It usually does not go away on its own and requires immediate medical attention. Monitor for symptoms of DVT, including unexplained swelling, cramping, pain, or tenderness in one area of the body. If you are sedentary, set goals to increase your daily physical activity. Talk to your healthcare provider about any risk factors you might have and ways you can lower your risk of developing a DVT.
Frequently Asked Questions
How long can someone have a DVT without knowing?
Many people don't know they have a DVT until it causes a serious condition, like a pulmonary embolism, which occurs when a blood clot travels to the lungs and causes a blockage. See your healthcare provider immediately if you have symptoms of DVT, including redness, swelling, or tenderness in an area of the body.
Does DVT usually go away on its own?
Blood clots associated with DVT can dissolve on their own when the clots are small. A DVT may not go away on its own. It's important to know the signs of a DVT and seek medical attention right away.
Is a DVT an emergency?
A DVT is potentially life-threatening, especially if a blood clot breaks off and travels through the bloodstream. This can lead to complications, like pulmonary embolism, which occurs when a blood clot causes a blockage in the lungs.
Can you feel a blood clot move up your body?
Tenderness and pain can occur with a DVT. You may feel some discomfort or pain If a blood clot breaks off and travels through the bloodstream to an area like the lungs. A blockage in this area of the body can make it difficult to breathe.
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