Learn About Deep Vein Thrombosis/Blood Clots | American Lung Association

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Learn About Deep Vein Thrombosis/Blood Clots

Blood clotting is a normal process that prevents bleeding when a blood vessel is injured. When a blood clot forms in veins deep in the body it is called deep vein thrombosis (DVT). Most deep vein blood clots occur in the lower leg or thigh.

Key Facts

  • Blood clotting is normal but can be dangerous when inside a vein. Clots in veins deep in the body can break free, travel through the bloodstream and get stuck in the lungs, blocking blood flow.
  • Although most patients survive, these conditions can be serious and even deadly.
  • Treatment with blood thinners is usually effective.

What Is DVT/Blood Clots and How It Affects Your Body

Blood clots are a normal reaction to blood vessel injury and bleeding. Sometimes a blood clot can form in a vein deep in the body, which is called DVT. These clots can form anywhere in the body, but most commonly develop in the calf or thigh of the leg. A serious and potentially life-threatening complication of these blood clots is pulmonary embolism (PE). PE is when a deep vein clot breaks loose and travels through the blood stream, lodging in the arteries in the lungs and blocking blood flow to the lungs.

How Serious Is DVT

DVT can be life-threatening, but patients almost always survive. Prompt recognition and diagnosis can be lifesaving, as is prevention of other complications associated with this potentially fatal condition.


    This content was developed in partnership with the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.


    Approved by Scientific and Medical Editorial Review Panel. Last reviewed December 13, 2016.

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