Slideshows Images Quizzes
font size

DVT (Blood Clot in the Legs) Symptoms, Signs, and Treatment Guidelines

Medical Author:
Medical Editor:
Medical Editor:

Deep vein thrombosis (DVT) definition and facts

  • There are both superficial and deep veins in the limbs or extremities (arms and legs). A blood clot in the deep veins is a concern because it can cause life-threatening complications.
  • A blood clot (thrombus) in the deep venous system of the leg becomes dangerous if a piece of the blood clot breaks off or travels through the blood stream, through the heart, and into the pulmonary arteries forming a pulmonary embolism. A person may not have signs or symptoms of a small pulmonary embolism (blood clot in the lungs), but a large embolism can be fatal.
  • Risk factors for blood clot formation include immobility, a genetic tendency toward blood clotting, and injury to veins or adjacent tissues occurs.
  • Symptoms of DVT or blood clot in the leg include:
    • Pain
    • Swelling
    • Warmth
    • Tenderness
    • Redness of the leg or arm
  • Doctors diagnose the condition is with blood tests, and then is confirmed by ultrasound or other imaging tests.
  • Treatment of typically involves taking blood thinning medications (anticoagulants) unless you cannot take them (contraindicated). In that situation, an inferior vena cava filter is potentially considered.
  • Complications of DVT include pulmonary embolism (PE) and post-phlebitic syndrome.
  • There are other types of thrombosis such as:
    • Cerebral venous thrombosis (CVT)
    • Portal vein thrombosis
    • Cavernous sinus thrombosis

What is DVT?

A deep vein thrombosis, or DVT describes a blood clot  (thrombosis) that forms in the deep veins located in the arm or leg. It is important to know the body's anatomy and function to understand why clots form in veins and why they can be dangerous.

  • Arteries have thin muscles within their walls to be able to withstand the pressure of the heart pumping blood to the far reaches of the body. Veins don't have a significant muscle lining, and there is nothing pumping blood back to the heart except physiology. Blood returns to the heart because the body's large muscles squeeze the veins as they contract in their normal activity of moving the body. The normal activities of moving the body returns the blood back to the heart. Being mobile causes this blood return system to fail, and the resulting stagnated blood may clot.
  • There are two types of veins in the arm or leg; superficial veins and deep veins. Superficial veins lie just below the skin and are easily seen on the surface. Deep veins, as their name implies, are located deep within the muscles of the extremity. Blood flows from the superficial veins into the deep venous system through small perforator veins. Superficial and perforator veins have one-way valves within them that allow blood to flow only in the direction of the heart when the veins are squeezed.
  • A blood clot (thrombus) in the deep venous system of the leg or arm, in itself, is not dangerous. It becomes potentially life-threatening when a piece of the blood clot breaks off and embolizes, travels through the circulation system through the heart, and enters into one of the pulmonary arteries and becomes lodged. This can prevent blood from flowing properly through the lung and decreasing the amount of oxygen absorbed and distributed back to the body.
  • Diagnosis and treatment of a DVT is meant to prevent pulmonary embolism.
  • Blood clots in the superficial veins do not pose a danger of causing pulmonary emboli because the perforator vein valves act as a sieve to prevent clots from entering the deep venous system. They are usually not at risk of causing pulmonary embolism.

What does a blood clot in the leg look like?

Picture of how red blood cells and platelets form a blood clot
Picture of how red blood cells and platelets form a blood clot

What causes DVT?

Blood is meant to flow. If it becomes stagnant, there is a potential for it to clot. The blood in veins constantly forms microscopic clots that are routinely broken down by the body. If the balance of clot formation and clot breakdown is altered, significant clotting may occur. A thrombus can form if one or a combination of the following situations.


  • Prolonged travel and sitting, such as long airplane flights ("economy class syndrome"), car, or train travel
  • Hospitalization
  • Surgery
  • Trauma to the lower leg with or without surgery or casting
  • Pregnancy, including 6-8 weeks post-partum after delivery of the baby
  • Obesity

Coagulation of the blood faster than usual (hypercoaguability)

  • Medications such as birth control pills (oral contraceptives), for example, Ortho-Novum, Yaz, Yasmin, Microgestin, Kelnor, and other estrogens
  • Smoking
  • Genetic or hereditary predisposition to clot formation
  • Increased number of red blood cells (Polycythemia)
  • Cancer
  • Trauma to the vein
  • Fracture to the leg or arm
  • Bruised leg or arm
  • Complication of an invasive procedure of the vein
Medically Reviewed by a Doctor on 7/3/2017


Women's Health

Find out what women really need.

Use Pill Finder Find it Now See Interactions

Pill Identifier on RxList

  • quick, easy,
    pill identification

Find a Local Pharmacy

  • including 24 hour, pharmacies

Interaction Checker

  • Check potential drug interactions
Search the Medical Dictionary for Health Definitions & Medical Abbreviations
Atrial Fibrillation Quiz

Health Solutions From Our Sponsors