Deep venous thrombosis


Deep venous thrombosis is a condition that occurs when a blood clot forms in a vein deep inside a part of the body. It mainly affects the large veins in the lower leg and thigh, but can occur in the deep veins in the arms.

Alternative Names

DVT; Blood clot in the legs; Thromboembolism; Post-phlebitic syndrome; Post-thrombotic syndrome


Deep vein thrombosis (DVT) is most common in adults over age 60. But, it can occur at any age. When a clot breaks off and moves through the bloodstream, this is called an embolism. An embolism can get stuck in the brain, lungs, heart, or other area, leading to severe damage.

Blood clots may form when something slows or changes the flow of blood in the veins. Risk factors include:

  • A pacemaker catheter that has been passed through the vein in the groin
  • Bed rest or sitting in one position for too long such as plane travel
  • Family history of blood clots
  • Fractures in the pelvis or legs
  • Giving birth within the last 6 months
  • Pregnancy
  • Obesity
  • Recent surgery (most commonly hip, knee, or female pelvic surgery)
  • Too many blood cells being made by the bone marrow, causing the blood to be thicker than normal (polycythemia vera)
  • Having an indwelling (long-term) catheter in a blood vessel

Blood is more likely to clot in someone who has certain problems or disorders, such as:

  • Cancer
  • Certain autoimmune disorders, such as lupus
  • Cigarette smoking
  • Conditions that make it more likely to develop blood clots
  • Taking estrogens or birth control pills (this risk is even higher with smoking)

Sitting for long periods when traveling can increase the risk of DVT. This is most likely when you also have one or more of the risk factors listed above.


DVT mainly affects the large veins in the lower leg and thigh, almost always on one side of the body. The clot can block blood flow and cause:

  • Changes in skin color (redness)
  • Leg pain
  • Leg swelling (edema)
  • Skin that feels warm to the touch

Exams and Tests

Your health care provider will perform a physical exam. The exam may show a red, swollen, or tender leg.

The two tests that are often done first to diagnose a DVT are:

  • D-dimer blood test
  • Doppler ultrasound exam of the area of concern

Blood tests may be done to check if you have an increased chance of blood clotting, including:

  • Activated protein C resistance (checks for the Factor V Leiden mutation)
  • Antithrombin levels
  • Antiphospholipid antibodies
  • Complete blood count (CBC)
  • Genetic testing to look for mutations that make you more likely to develop blood clots, such as the prothrombin G20210A mutation
  • Lupus anticoagulant
  • Protein C and protein S levels


Your doctor will give you medicine to thin your blood (called an anticoagulant). This will keep more clots from forming or old ones from getting bigger.

Heparin is usually the first drug you will receive.

  • If heparin is given through a vein (IV), you must stay in the hospital.
  • Newer forms of heparin can be given by injection under your skin once or twice a day. You may not need to stay in the hospital as long, or at all, if you are prescribed this newer form of heparin.

Depending on your medical history, fondaparinux may be recommended by your doctor as an alternative to heparin.

A blood-thinning drug, for example warfarin (Coumadin), is usually started along with heparin.

  • Warfarin is taken by mouth. It takes several days to fully work.
  • Heparin is not stopped until the warfarin has been at the right dose for at least 2 days.
  • You will most likely take warfarin for at least 3 months. Some people must take it longer, or even for the rest of their lives, depending on their risk for another clot.

When you are taking warfarin, you are more likely to bleed, even from activities you have always done. If you are taking warfarin at home:

  • Take the medicine just the way your doctor prescribed it.
  • Ask the doctor what to do if you miss a dose.
  • Get blood tests as advised by your doctor to make sure you are taking the right dose.
  • Learn how to take other medicines and when to eat.
  • Find out how to watch for problems caused by the drug.

You will be given a pressure (compression) stocking to wear on your leg or legs. A pressure stocking improves blood flow in your legs and reduces your risk for complications from blood clots. It is important to wear it every day.

In rare cases, you may need surgery if medicines do not work. Surgery may involve:

  • Placing a filter in the body's largest vein to prevent blood clots from traveling to the lungs
  • Removing a large blood clot from the vein or injecting clot-busting medicines

Follow any other instructions you are given to treat your DVT.

Outlook (Prognosis)

DVT often goes away without a problem, but the condition can return. Some people may have long-term pain and swelling in the leg called post-phlebitic syndrome.

You may also have pain and changes in skin color. These symptoms can appear right away or you may not develop them for 1 or more years afterward. Wearing compression stockings during and after the DVT may help prevent this problem.

Blood clots in the thigh are more likely to break off and travel to the lungs (pulmonary embolus) than blood clots in the lower leg or other parts of the body.

When to Contact a Medical Professional

Call your health care provider if you have symptoms of DVT.

Go to the emergency room or call the local emergency number (such as 911) if you have DVT and you develop:


To prevent deep vein thrombosis:

  • Wear the pressure stockings your doctor prescribed.
  • Moving your legs often during long plane trips, car trips, and other situations in which you are sitting or lying down for long periods.
  • Take blood thinning medicines your doctor prescribes.
  • DO NOT smoke. Talk to your doctor if you need help quitting.


Dupras D, Bluhm J, Felty C, et al. Institute for Clinical Systems Improvement. Venous thromboembolism diagnosis and treatment. Updated January 2013. Accessed February 26, 2015.

Guyatt GH, Akl EA, Crowther M, et al. Executive Summary: Antithrombotic Therapy and Prevention of Thrombosis. 9th ed. American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. 2012;141(2 suppl):7s-47s. PMID: 22315257

Kline JA. Pulmonary embolism and deep vein thrombosis. In: Marx JA, Hockberger RS, Walls RM, et al., eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier Mosby; 2014:chap 88.

Review Date: 2/13/2015
Reviewed By: Rita Nanda, MD, Assistant Professor of Medicine, Section of Hematology/Oncology, University of Chicago Medicine, Chicago, IL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
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