Thrombosis is the medical term for blood clot formation. Older age, pregnancy, and smoking are among the risk factors. Prompt medical attention is needed to avoid complications.

The formation of a blood clot, called “thrombosis,” is a potentially serious condition that develops when a mass of blood cells and other substances in your bloodstream stick together. Blood clot formation is called “arterial thrombosis” when it develops in an artery and “venous thromboembolism” when it develops in a vein.

Blood clots can lead to serious complications, such as:

Many factors may increase your chances of developing a blood clot, such as:

  • long periods of physical inactivity
  • injury to a blood vessel
  • smoking
  • pregnancy

Read on to learn more about blood clots, including types, symptoms, and treatment options.

The medical name for a blood clot is a “thrombus.” Thrombosis is the formation of a blood clot. A blood clot can break away from the wall of your blood vessel and block the flow of blood. This blockage can cause serious complications that vary depending on where the blood clot becomes lodged.

A similar term is an “embolism.” An embolism is any mass that moves through your blood vessels and becomes lodged in a blood vessel. An embolism is usually caused by a thrombus but can also be caused by other substances such as:

  • fat
  • air bubbles
  • fluids

Arterial thrombosis is the leading cause of death worldwide.

The lifetime risk of developing venous thromboembolism is about 8% in the United States, and about 1 in 5 people die within a year of having their condition diagnosed, often from the underlying health condition that led to the blood clot.

“Thrombosis” is the medical term for the formation of a blood clot.

Doctors and healthcare professionals often use the terms “thrombosis” and “thromboembolism” when describing blood clots because these terms describe the condition more precisely.

Blood clots are divided into different types depending on where they form:

  • Venous thromboembolism: Venous thromboembolisms occur in the blood vessels that carry blood to your heart, called “veins.” This kind of thrombosis usually occurs in your legs. Types of venous thromboembolism include:
    • Deep vein thrombosis: A deep vein thrombosis may occur when a blood clot forms in a deep vein, usually in your legs.
    • Pulmonary embolism: A pulmonary embolism is a sudden blockage in one of the blood vessels that sends blood to your lungs. These embolisms usually occur when a blood clot from your lower body travels to your lungs.
  • Arterial thrombosis: An arterial thrombosis occurs when a blood clot forms in an artery. An artery is a blood vessel that carries blood away from your heart.

The symptoms of a blood clot vary depending on where it’s located. Symptoms may include the following:



Arm or leg

  • redness
  • warmth
  • swelling
  • tenderness
  • pain that onsets suddenly or slowly


When to seek emergency medical attention

It’s important to get emergency attention, by calling 911 or local emergency services, if you or somebody you’re with:

  • has throbbing or cramping pain in an arm or leg
  • has swelling and warmth in an arm or leg
  • experiences sudden breathlessness
  • becomes unconscious
  • has sharp chest pain that may get worse on inhalation
  • has a sudden cough or is coughing up blood
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Blood clots form when your blood cells and other substances in your bloodstream form a semisolid mass. Blood clots become more common with increasing age. The yearly risk of developing a blood clot has been estimated as:

  • 1 in 100,000 for children
  • 1 in 10,000 for young adults
  • 1 in 1,000 for middle age adults
  • 1 in 100 for older adults

Risk factors for blood clots include:

Learn more about risk factors for blood clots.

The best treatment for a blood clot depends on the type of blood clot you have and its severity.

Venous thromboembolism

Venous thromboembolism doesn’t always require treatment, but up to 100,000 people die of deep vein thromboses each year in the United States. It’s important to call 911 or your local emergency services for emergency medical attention to avoid potentially serious complications.

If a doctor decides that treatment is necessary, the first-line option is usually anticoagulants. These medications are also called “blood thinners.” Common blood thinners include warfarin or heparin.

These medications stop new blood clots from forming. You may have to take blood thinners for a range of several months to your remaining lifetime.

Severe blood clots may be treated with medications called “thrombolytics” to dissolve the blood clot.

If medications alone aren’t effective, you may need catheter-assisted blood clot removal. This type of surgery involves removing the blood clot with a long tube inserted into one of your blood vessels.

Some people receive a vena cava filter to catch new blood clots before they reach their lungs.

Arterial thrombosis

Arterial thromboses are primarily treated with:

  • thrombolytics to dissolve blood clots
  • embolectomy surgery to remove the blood clot
  • a type of surgery, called an “angioplasty,” to widen the affected artery
  • surgery, such as a coronary artery bypass graft, to divert blood around the blocked artery

A thrombosis occurs when a blood clot forms in your blood vessels. A blood clot is medically known as a “thrombus.” Blood clots can cause serious complications, depending on the blood vessel in which they become lodged.

It’s crucial to get immediate medical attention if you have symptoms of a blood clot, such as a red, swollen, or warm limb. Medical attention is especially important if you have recently had vascular surgery or have other risk factors for blood clots.