How to Prevent Deep Vein Thrombosis (DVT)

Those in your legs can be as lethal as clots in your brain or heart

Published: January 2013

Hillary Clinton, back at work, after recovering from a blood clot caused by a concussion.
Photo: Department of State via Getty Images

Blood clots can be lifesaving when they stop bleeding caused by a cut or injury. But they can be deadly if they form when and where they aren’t needed. 

That’s why the news in late December 2012 that Secretary of State Hillary Clinton had a clot in a vein between her brain and skull was so worrisome. If it had seriously interfered with the flow of blood in her brain, she could have had a stroke. When a clot blocks blood to the heart, it can cause a heart attack. And even a clot that forms deep in the veins in the pelvis or legs—a so-called DVT, or deep-vein thrombosis—can be fatal if it breaks into smaller pieces and travels through the bloodstream to the lungs.

Clinton had a blood clot behind her knee back in 1998. Thankfully, that clot—like the more recent one—was identified and treated early. But each year, as many as 100,000 Americans die from a pulmonary embolism, or a blood clot from the lower body that lodges in the lungs, depriving the organ of oxygen.

The good news is that deep-vein thrombosis and pulmonary embolism can usually be treated, if you recognize the signs and symptoms early. Even better, most blood clots can be prevented, if you take some simple, common-sense steps.

The danger

A pulmonary embolism, above, can occur when a clot from the legs travels to the lungs.

A clot that forms in a vein near the surface of the skin typically causes little more than an itching or burning sensation. But 600,000 people each year in the U.S. experience deep-vein thrombosis, which can lead to painful swelling and inflammation, as the clot slows or blocks the flow of blood back to the heart.

Such clots must be treated to prevent them from scarring and discoloring your skin, and to avoid painful, disabling, and hard-to-treat skin ulcers. More important, treatment is necessary to prevent a clot in the legs or pelvis from breaking up and traveling to the lungs. If those clot pieces, called emboli, lodge in the lungs, they can prevent those organs from getting enough oxygen-carrying blood, killing tissue, and making it hard for you to breathe. Left untreated, pulmonary emboli kill about 30 percent of people who experience them.

Who's at risk?

Clinton’s latest blood clot was caused by a concussion she suffered when she hit her head after fainting, according to the U.S. Department of State. Her age, 65, also puts her at higher risk of clots. Other risk factors include: 

  • Sitting for longer than 6 to 8 hours, such as during a trip in a car or plane. 
  • Having limited mobility due to a medical issue, surgery, or paralysis. 
  • Having an injured vein from a bone fracture, severe muscle injury, trauma, or major surgery (especially involving the abdomen, pelvis, hip, or legs). 
  • Having a tube placed in a vein for medication or other treatment, such as a central venous catheter. 
  • Having heart failure or cancer in the abdomen. 
  • Being pregnant, taking birth-control pills, or taking prescription hormones for menopause symptoms. 
  • Having a family history of clots.
  • Being overweight or obese, having high blood pressure, or being a smoker. 
  • Having certain genetic or inherited blood-clotting disorders, such as Factor V Leiden.

Prevent clots

About half of the people with deep-vein thrombosis don’t have symptoms. Most people, for example, don’t notice blood clots in the pelvis. So the best way to protect yourself is to try to prevent them by following a healthy lifestyle, including exercising regularly, losing excess weight, and not smoking. 

It’s also important to avoid long periods sitting or lying down, which can allow blood to pool and form clots. Walking or otherwise working the lower leg muscles combats that by propelling blood upward toward the heart. If you’re stuck on a long car or plane ride and can’t get up, you can still exercise your legs while in your seat by pumping your feet back and forth. If you’re confined to a bed because of surgery or illness, get up and move around as soon as your doctor clears you to do so. And talk to your doctor about preventing blood clots before you are admitted to a hospital or have surgery, particularly if you are at risk for them. Anticoagulant medication, such as heparin, may be given after surgery to help prevent a blood clot.

Know the warning signs

Clots can form in the legs, arms, or pelvis, and then travel to the lungs.

The first step in preventing dangerous complications is to be alert for symptoms. Here’s what to watch for.

Deep-vein thrombosis: Unexplained swelling, pain, tenderness, or redness in the pelvis or legs. When a clot forms in the arm, it's called venous thrombosis. In either case, call a doctor promptly.

Pulmonary embolism: Difficulty breathing, a rapid or irregular heartbeat, chest pain or discomfort, coughing up blood, and feeling faint. Go to an emergency room or call 911.

Doctors should perform special tests to make sure that your symptoms stem from a deep-vein thrombosis or a pulmonary embolism and not another health problem that causes similar symptoms. For example, muscle strains and tendon tears in the calf can mimic the symptoms of deep-vein thrombosis. And a pulmonary embolism can sometimes be confused with a heart attack or pneumonia.

Deep-vein thrombosis is often diagnosed with a blood test known as a D-dimer and using ultrasound, which can assess the flow of blood in veins. If your doctor suspects a clot in your lungs, you might undergo a chest computerized tomography (CT) scan with a simultaneous pulmonary angiogram. That combination is the gold standard for the diagnosis of pulmonary emboli.

Get the right treatment

If you have a deep-vein thrombosis, your doctor should usually prescribe either heparin or the related drug fondaparinux (Arixtra and generic). That is often followed by warfarin (Coumadin, Jantoven, and generic). Although those medications are often referred to as blood thinners, they don’t actually thin the blood. Instead, they impair the clotting process and can prevent existing clots from growing larger. But they can also cause life-threatening internal bleeding (see box below).

You probably won’t receive intravenous medication for more than a few days. After that, you should usually be switched to self-injections of heparin and warfarin pills. Warfarin takes up to several days to work but once it becomes effective, you can usually stop taking heparin, though you may continue taking warfarin for several months or longer.

Warfarin is very effective but poses a risk of serious internal bleeding while you are taking it, so blood tests are required at least once a month to make sure it’s continuing to work properly and that you’re not at risk of bleeding. Uncontrolled bleeding caused by the drug leads to an estimated 43,000 visits to emergency rooms each year.

Some foods and beverages can reduce warfarin’s effectiveness. Specifically, you should avoid eating unusually large amounts of food high in vitamin K, such as broccoli, brussel sprouts, collard greens, kale, and spinach. Also be sure to tell your doctor about any medications or dietary supplements you take, because many drugs and supplements can interact with warfarin.

Medical compression stockings are commonly used to prevent further blood clots after suffering a DVT, and after any surgery that might require bed rest. The stockings, which stretch from the foot to the knee, can help relieve pain and swelling. They’re tight at the ankle and looser near the knee, to keep blood from pooling and forming a clot in the lower leg. Some people wear them for two years or longer after first having a clot.

A pulmonary embolism is a medical emergency. If the clot is life-threatening, doctors in the hospital usually give the patient medications called thrombolytics, such as alteplase (Activase), to try to dissolve it. Those medications carry a risk of serious sudden internal bleeding, so they’re used only in life-threatening situations. In some cases, doctors might need to thread a flexible tube, or catheter, through a vein in your groin or arm to the clot. The doctor can then try suction to remove the clot or deliver thrombolytic medication through the catheter to dissolve it. In rarer cases, doctors might have to perform surgery to remove the clot.

After treatment for pulmonary embolism, you’ll probably have to take the same drugs that people take after a deep-vein thrombosis.

Treatment details

There are a variety of alternatives for treating a blood clot, depending on a number of factors, including its location in the body, the type of clot, and the patient’s overall health. Listed below are some of the more common ones.

Treatment Comments
Compression stockings Insurance might not cover them, so be sure to check with your provider.
Heparin Given intravenously at a hospital or by injection. Carries a higher risk of internal bleeding than low-molecular-weight heparin.

Low-molecular-weight heparin

Dalteparin (Fragmin), enoxaparin (Lovenox and generic)

There’s a risk of internal bleeding; Report any unusual bleeding or bruising to your doctor. 

Selective factor Xa inhibitors

Fondaparinux (Arixtra and generic), rivaroxaban (Xarelto)

Both drugs reduce the risk of blood clots more than low-molecular-weight heparin, but may also increase risk of bleeding. Fondaparinux is given intravenously or by injection; Rivaroxaban is available as a pill.
Surgery Done only in rare cases.


Includes alteplase (Activase)

Used to treat life-threatening blood clots in the lungs.


Coumadin, Jantoven, and generic

To reduce the risk of internal bleeding, don’t start or stop any medications or dietary supplements without a doctor’s approval. Eat a consistent diet and avoid eating unusually large amounts of food high in vitamin K, such as broccoli, collard greens, and kale. Report any unusual bleeding or bruising to a doctor. 

Drug side effects to watch for

Contact your doctor immediately if you notice any of these side effects after taking anticoagulant drugs.

  • Prolonged bleeding from cuts, your gums, or nose.
  • Unusual bruising.
  • Pink or brown urine or red or tar-black stools.
  • Pain or a purple color in your toes.
  • For women, a heavier than normal menstrual flow.

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