Deep vein thrombosis (DVT)

Deep vein thrombosis, or DVT, happens when a blood clot forms in a vein deep inside your body, most often in the leg. Left untreated, a DVT blood clot can break loose and travel to your lungs, causing a serious complication called a pulmonary embolism. With prompt diagnosis and the right DVT treatment, most people recover well and lower their risk of future complications.

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An illustration of legs detailing the venous system.

Anatomy of deep veins

Your veins carry blood back to your heart, relying on one-way valves and the movement of your muscles to keep blood flowing in the right direction. Deep veins, which run through your muscles, handle most of this blood flow, especially in your legs.

When blood flow slows down or blood pools in these deep veins, it can thicken and form a clot. Deep vein thrombosis most often develops in the lower leg, thigh or pelvis, though it can also occur in an arm. A clot can partially or fully block blood flow, causing swelling and pain in the affected area.

Overview

Symptoms

DVT symptoms can develop gradually or appear suddenly, and some people notice no symptoms at all. Common signs include:

Swelling in the affected leg or arm
Pain or tenderness, often starting in the calf
Skin that feels warm to the touch near the affected area
Red or discolored skin over the clot
A heavy or achy feeling in the affected limb

If you notice sudden shortness of breath, chest pain, or a rapid heartbeat, seek emergency care right away. These can be signs that a clot has traveled to the lungs.

Causes

DVT develops when something slows or disrupts normal blood flow through the deep veins, allowing a clot to form. Common causes include:

Prolonged sitting or immobility, such as during long flights or car rides
Extended bed rest after surgery, illness or injury
Damage to a vein from injury or surgery
Conditions that make your blood more likely to clot

In some cases, more than one factor contributes to a blood clot in the leg or arm.

Risk factors

Certain factors can increase your likelihood of developing DVT, though having one or more of these doesn't mean you'll develop this condition:

Age, especially over 60
A previous DVT or family history of blood clots
Extended periods of inactivity, such as long trips or bed rest
Recent surgery, especially orthopedic or abdominal procedures
Pregnancy or hormone-based medications such as birth control or hormone therapy
Smoking
Obesity
Certain cancers or cancer treatments

Knowing your risk factors can help you and your care team make informed decisions about prevention and monitoring.

Diagnosis

Diagnosing DVT typically starts with a discussion of your symptoms and medical history, followed by a physical exam to check for swelling, tenderness and skin changes. Imaging and lab tests can confirm the diagnosis. Common tests include:

Ultrasound, which uses sound waves to check blood flow and detect clots in the veins
D-dimer blood test, which measures a substance released when a clot breaks down
Venography, an imaging test that uses contrast dye to show blood flow through the veins in more complex cases

A medical illustration of the circulatory system to show an example of deep vein thrombosis.

Understand DVT and when to seek care

Knowing what DVT is, what to watch for and how it's treated puts you in a stronger position to get the right care quickly.

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