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Deep Vein Thrombosis (DVT)

Last Updated: Mar 1, 2019


Deep vein thrombosis, or DVT, occurs when a blood clot (also called a thrombus) forms in a large vein of the body. Clots form when blood pools, thickens and clumps together. DVT is most common in the thigh, lower leg and pelvis, though it can also occur in the arm.

By itself, DVT is not usually life-threatening. However, clotting in a large vein blocks some or all blood flow through that vein, causing blood to build up behind the clot. This can damage the vein, resulting in a chronic (long-term) condition called post-thrombotic syndrome (PTS). PTS symptoms include pain, swelling, discoloration and sores on the legs.

There is also a chance that the clot could break away from the wall of the vein and travel through the blood vessels. This can cause a life-threatening complication called pulmonary embolism (PE) in which a clot lodges in one of the main arteries of the lungs, preventing the flow of oxygenated blood to the body.

DVT isn’t always diagnosed, so experts aren’t sure how common it is. The Centers for Disease Control estimates that 1-2 people per 1,000 develop DVT each year. In people over 80, this number may be as high as one in 100.

In addition, an estimated 60,000 to 100,000 Americans die from PE each year. Most (but not all) of these cases are caused by DVT.

Causes and Risk Factors

pulmonary arteries

Any factor that interferes with circulation or promotes clotting can increase a person’s risk for DVT, and many cases have multiple causes.

Inactivity is a major cause of DVT. Under normal circumstances, the contractions of the calf muscles as a person walks help circulate blood through the legs. But when a person is bedridden or sits for long periods during airline or car travel, the blood may pool in the legs, resulting in clots.

Some medical conditions and their treatments increase the risk of blood clots. Examples include:

Women with elevated estrogen levels are at increased risk for clots. Risk factors include the use of some oral contraceptives and hormone replacement therapy. Risk is also elevated during pregnancy and for six weeks after giving birth.

Other risk factors for DVT include:


It’s possible to have DVT without knowing it. In fact, doctors estimate that symptoms are present in only about half of all cases. These include:

DVT symptoms usually occur on just one side of the body.

PE symptoms include:


Because of the potential for serious complications, it’s important to seek immediate medical attention if you have symptoms of DVT or PE. Call your doctor, or go to the nearest emergency room if your doctor is not available.

To diagnose DVT, a physician typically performs the following tests:


Treatment of DVT has several goals:

Depending on the severity of the condition and risk of complications, patients may be admitted to the hospital for treatment.

DVT is treatable, especially when detected early. However, PE can be quite serious, resulting in permanent lung damage and death. In fact, sudden death is the first symptom in about one-quarter of people who develop PE.

About 30-50 percent of people diagnosed with DVT will later develop post-thrombotic syndrome, and about one third will experience a recurrence of DVT within 10 years.


DVT and PE are often preventable. The following steps can help reduce your risk:


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Tina Shahian, PhD

Tina is a writer for Innerbody Research, where she has written a large body of informative guides about health conditions.


A communication specialist in life science and biotech subjects, Tina’s successful career is rooted in her ability to convey complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. Tina Shahian’s Linkedin profile.


In her spare time, Tina enjoys drawing science-related cartoons.