Deep Vein Thrombosis (DVT)/Blood Clots

Last Updated 11/02/2020

Authors:Jason Golbin, DO, MS, FCCP; Aleksander Shalshin, MD, MS, FCCP

About Deep Vein Thrombosis (DVT)/Blood Clots

Blood clots are the body’s way of stopping blood loss. If you cut your finger, the blood in the area of injury clumps together, or clots. The clot stops the blood from flowing from your finger and is the first step toward healing.

Clots are formed by blood cells and other factors in the blood. Blood clots aren’t a problem unless they block the flow of blood to where it belongs. Blood carries oxygen to all parts of the body, but blood clots can keep blood and oxygen from reaching their destination. Without enough oxygen, body parts can be damaged. Heart muscle or brain tissue that doesn’t get enough oxygen, for instance, begins to die. That hurts the functioning of the body.

Key facts about Deep Vein Thrombosis
  • A vein is a blood vessel that carries blood from the body back to the heart. The word thrombosis means clot. So, a deep vein thrombosis (DVT) is a blood clot that forms in a vein deep inside the body.
  • DVTs typically form in a leg. There, it blocks important blood flow.
  • These blood clots can break loose and travel to other parts of the body, such as the heart, brain, or lung.
  • A blood clot that travels to the lungs, blocking the flow of blood and oxygen, is called a pulmonary embolism (PE). A PE is a potentially life-threatening event.

DVT and PE affect an estimated 350,000 to 600,000 Americans each year, contributing to at least 100,000 deaths annually. Most occur in people who have other illnesses or are recovering from surgery or a serious accident.

The best way to avoid being harmed by a DVT or PE is to know the symptoms. Quick diagnosis and treatment can help you avoid the most damaging outcomes.

Symptoms of DVT

DVTs typically occur in the legs. The most common symptoms of DVT include:

  • Swelling in the affected leg;
  • Pain in the leg, which may feel like cramping in the calf;
  • Warmth in the affected area; and
  • Redness or other changes in skin color, such as the skin turning paler or more blue than normal.

DVT can also occur without any noticeable symptoms.

Symptoms of a PE, a blood clot that has traveled to the lungs, include:

  • Difficulty breathing;
  • Sharp chest pain that worsens after taking deep breaths;
  • Coughing up blood; and
  • Light-headedness, fainting, and unconsciousness (for large clots).

Symptoms of a PE can occur suddenly and without warning. PE symptoms always require prompt medical assessment.

If you have these symptoms, get emergency help right away.

What causes DVTs?

DVTs have many causes. Some of the most common causes and contributing factors include:

  • Sitting for long periods of time, such as during long-distance travel or long-term bed rest. When your body remains in one position for a long time, blood is more likely to pool and clot.
  • Inheriting a blood-clotting disorder. Sometimes, clotting problems run in families. Factor V Leiden thrombophilia is an example of a disorder that increases the chance of developing harmful blood clots and DVTs.
  • Injury or surgery. When the inside lining of a blood vessel is damaged, blood is more likely to clot.
  • Pregnancy. High hormone levels during pregnancy make the blood prone to clotting. Pregnancy also decreases blood flow to the lower legs, increasing the risk of DVT. The risk of developing a DVT remains high in the first 6 weeks after you give birth.
  • Estrogen use, including the use of oral contraceptives (birth control pills). Hormone replacement therapy (HRT) and birth control pills both increase the risk of blood clots and DVTs. Smoking further increases this risk, which is why birth control pills aren’t recommended for women who smoke.
  • Cancer. Researchers and health care providers have noticed a link between certain types of cancers and blood clots. People with cancers of the brain, ovaries, pancreas, colon, stomach, lung, kidney, or liver are at increased risk of developing DVTs. Lymphoma and leukemia, 2 types of blood cancer, also increase the risk of DVT.
  • Advanced age. Most DVTs occur in people over the age of 60, although they can occur at any age.
  • Obesity. People who are obese face more than twice the risk of developing a DVT or PE than people who are not obese. Women who are obese and take birth control pills have an even higher risk of DVT.
  • A history of DVT or PE. A previous DVT or PE dramatically increases the risk of another DVT.

What are risk factors for DVT?

Some of the most significant risk factors for DVT are:

  • Being inactive for long periods. When you stay in bed after surgery or a serious illness or you sit for a long time on a flight or car trip, blood pools in your legs. This increases the chance of a DVT;
  • Recent surgery that involved the legs, hips, belly, or brain. Major surgeries, like a C-section, increase the risk of DVTs more than minor surgery, such as having your tonsils removed;
  • Diseases such as cancer, heart failure, stroke, or a severe infection;
  • Blood-clotting disorders; and
  • Smoking.

Some factors that increase your risk for DVT—such as an inherited blood-clotting disorder or advanced age—are out of your control. Other risk factors—such as smoking—are in your control.

Decrease your risk of developing a DVT by maintaining a healthy weight, staying active, and not smoking. If you’re a woman of childbearing age, consider nonhormonal methods of birth control, such as condoms, especially if you have other risk factors for DVT.

Complications of DVT

PE is the most serious complication of DVT. PE occurs when a DVT travels through the bloodstream from the leg to a lung. The clot can lodge in the pulmonary artery, the main blood vessel supplying oxygen to the lungs. A PE can cause difficulty breathing and an irregular heartbeat. A clot may be so large that it blocks the flow of blood from the heart, which can lead to heart failure, shock, and death.

The signs and symptoms of a PE include:

  • Sudden shortness of breath and rapid breathing, even when resting;
  • Coughing up blood;
  • Chest pain; and
  • Sudden rapid heart rate.

A PE is a medical emergency. If you or anyone you know experiences any of these symptoms, call 911 and seek emergency medical treatment immediately. Prompt medical treatment can dissolve the blood clot and restore blood flow and oxygen delivery to the lungs.

Another complication of DVT is called post-thrombotic syndrome. In this syndrome, if a clot stays in a vein for too long, it can damage the vein and force blood to pool in the leg. Signs and symptoms of post-thrombotic syndrome include:

  • Pain;
  • Swelling;
  • Darkened skin color;
  • Skin ulcers;
  • Varicose veins; and
  • Recurring DVT or PE.

Approximately 2 out of 3 people who develop a DVT will also develop post-thrombotic syndrome.

Diagnosing DVT

To diagnose a DVT, your health care provider will ask you about your symptoms and conduct a thorough physical examination. If a DVT is suspected, your provider will likely do an ultrasound. During an ultrasound, a technician runs an probe down the outside of your leg, pressing gently, to look for clots.

Your health care provider may also order blood tests. A D-dimer test is often done in people with a suspected clot. If the test result is negative (normal), you probably don’t have a blood clot. A positive (abnormal) test result doesn’t always mean a blood clot is present, however. Additional testing, such as an ultrasound, is often needed to confirm or rule out a blood clot.

Blood tests can also be used to look for inherited blood-clotting disorders or other abnormalities that may increase the tendency to clot.

If your symptoms suggest that you have a PE, your health care provider will take steps to help you breathe better and move quickly to see if a blood clot is responsible for your symptoms. Tests for PE include:

  • Lung scan. A lung scan, also known as a ventilation-perfusion (VQ) lung scan, is actually a combination of 2 tests. One test looks at how well oxygen is moving through your lungs. The other looks at the flow of blood, called perfusion, to your lungs.

    During the ventilation scan, you breathe in (or inhale) a special gas through a mask. A scanner tracks the flow of the gas through your lungs. Before the perfusion exam, a health care provider injects a radioactive solution into your vein. During the scan, you lie under a special scanner that tracks the flow of the solution through the pulmonary arteries that carry blood through the lungs.
  • Computed tomography. A CT scan can help your provider look for a PE. Before a CT scan, a provider injects a special dye into a vein in your arm. The dye makes the blood vessels in your legs and lungs show up on the CT scan. You lie on a table during the test while a scanner rotates around you. The scanner takes pictures of you from many angles. A CT scan only takes a few minutes.
When should you see your health care provider?

Contact your provider if you have:

  • Sudden, unexplained shortness of breath;
  • Swelling in one of your legs;
  • Chest pain;
  • A feeling that your heart is racing;
  • A previous blood clot; or
  • A family history of DVT or PE.

Preparing for your appointment

Whether you go the emergency department or a doctor’s office, you should be prepared to talk about your medical history and current symptoms. If possible, gather the following information before you go:

  • Past medical history. Do you have any medical problems? How are they treated? Have you had any surgeries in the past? What kind?
  • List of medications. Make a list of all medications, supplements, and vitamins that you take. If you can, bring the bottles with you to your appointment. That way, your health care provider can see exactly what you’re taking at what doses.
  • Family history. Has anyone in your family ever had a DVT or PE? Is there a family history of a blood-clotting disorder?
  • Current symptoms. When did you first notice symptoms of a DVT or PE? Is your leg affected? When did your symptoms occur? Have your symptoms changed over time? Has anything provided relief?

Treating DVT

The goal of DVT treatment is to prevent the complications that can occur with DVT. Because DVTs that occur below the knee don’t typically travel to other parts of the body, health care providers often monitor them with ultrasounds at follow-up appointments. At the same time, your health care provider will work to find the cause of the clot. He or she may suggest medical treatment to address the cause. Large DVTs and PEs are sometimes treated with medication that helps break apart the clot to restore blood and oxygen flow and decrease the risk of serious complications.

Medications to treat DVT

Medication that thin the blood and help prevent clotting, called anticoagulation therapy, is used to treat all DVTs and PEs. The medication also helps prevent new clots from forming while allowing the body to break down the clots that exist. Your provider may prescribe more than one anticoagulant because some work quickly while others take time to build up in the blood and become effective.

Heparin and low-molecular-weight heparin (LMWH)—commonly known as enoxaparin sodium, or Lovenox—are used in hospitals and health care settings to thin the blood soon after a DVT or PE is diagnosed. Heparin can be given intravenously (IV) or injected just beneath the skin. LMWH is given as a shot beneath the skin.

At the same time one of these medications is started, you may begin treatment with an oral (by mouth) anticoagulant. Oral anticoagulants take time to reach the right, or therapeutic, level in the blood. When the anticoagulant is therapeutic, you can stop heparin or LMWH treatment. You continue treatment with the oral anticoagulant.

The most common oral anticoagulant is warfarin. Warfarin has been around since 1954 and is routinely used to treat and prevent DVTs and PEs. It takes time to find the proper dose of warfarin. If you start treatment with warfarin, your health care provider will carefully monitor your blood. Your provider gives you blood tests and may change your dose of warfarin up or down to keep your blood “just right.”

Some people can’t take warfarin or aren’t able to return to their health care provider’s office for blood tests and dosage adjustments. If you can’t take warfarin for any reason, you may be a good candidate for treatment with one of the newer anticoagulants, such as:

  • Dabigatran, an oral anticoagulant taken as a pill. Dabigatran doesn’t require regular blood testing and is approved by the US Food and Drug Administration (FDA) to prevent stroke in patients with an irregular heartbeat.
  • Rivaroxaban, which the FDA approved in 2012. It comes in pill form and doesn’t require regular blood testing.
  • Apixaban, which the FDA approved in 2012. Like dabigatran and rivaroxaban, apixaban comes in pill form and doesn’t require regular blood tests.

Risks of anticoagulants

All blood-thinning medications increase the risk of bleeding. Contact your health care provider immediately if you notice any abnormal bleeding, such as:

  • Cuts that bleed profusely or don’t stop bleeding;
  • Blood in your bowel movements;
  • Heavier-than-normal menstruation; or
  • Blood-tinged or blackish sputum, phlegm, or vomit.

About 1% to 2% of people taking anticoagulants will develop serious bleeding. This bleeding may require a blood transfusion, and you may need to stop anticoagulation therapy.

Most people stay on anticoagulants for 3 to 6 months after a DVT or PE. People at high risk of repeated DVT and PE may be prescribed anticoagulants for life.

Some people cannot take anticoagulants. Those who have had a severe injury may be at high risk of serious bleeding with blood thinners. Others may have a PE even when taking medications to prevent them. In these situations, a doctor may place a filter in the major vein leading from the legs to the heart, called the inferior vena cava. This filter catches clots and prevents them from reaching the lungs.

Managing DVT

Because anticoagulants increase the risk of bleeding, be careful while shaving and working with sharp tools. Avoid activities that can cause injuries or open wounds. Use a soft toothbrush, waxed dental floss, and electric razors.

Some people who take anticoagulants wear medical alert bracelets to let first responders know that they’re taking such medication.

Certain foods interfere with the function of warfarin in the body. If you’re taking warfarin, carefully monitor your diet, and keep it consistent from day to day. Foods that can affect warfarin include green leafy vegetables, such as kale, green cabbage, broccoli, and Brussels sprouts; cranberry juice; green tea; mayonnaise; and fish oil.

You don’t have to avoid these foods completely. Just eat them in small, consistent amounts. Your health care provider may refer you to a dietician, who can help you figure out how to balance your diet with your medication. Be completely honest about your food likes, dislikes, and habits so that your provider and dietician can develop an eating plan that works for you.

Preventing DVT and PE

You can help decrease your risk of developing DVTs. If your health care provider suspects that you’re at increased risk for a DVT or blood clot for any reason—genetics, upcoming surgery, limited movement—he or she may recommend:

  • Preventive treatment with anticoagulants;
  • Elastic compression stockings. These stockings, which you wear on your legs, provide gentle, graduated pressure to keep blood from pooling in the legs. Compression stockings are custom fit and obtained by prescription. You put on stockings after waking and wear them throughout the day. You remove them to bathe and at bedtime.
  • Movement breaks on long trips. The overall risk of developing a DVT while traveling is low, but it increases on trips lasting long than 4 hours. Decrease your risk by moving and flexing your legs and periodically walking around. If you’re at high risk for developing a DVT or blood clot, your health care provider may recommend that you wear compression stockings while traveling.


A blood clot, DVT, or PE can be scary. A PE can be particularly startling because it may occur suddenly, without warning. Talking to friends and family members may be helpful. Journaling, or writing your thoughts down in a notebook or on a computer, can also help you process your feelings.

Learning more about your condition can help you feel in control. Ask your health care provider to explain anything you don’t understand. The more you know about blood clots, risk factors, treatment, and prevention, the better prepared you’ll be to select a treatment and prevention plan that fits your lifestyle.