What Is the Difference Between a Thrombus and a Blood Clot?

What are blood clots? What is a thrombus?

A thrombus is a blood clot that occurs in and occludes a vein while a blood clot forms within an artery or vein and it can break off and travel to the heart or lungs, causing a medical emergency.
A thrombus is a blood clot that occurs in and occludes a vein while a blood clot forms within an artery or vein and it can break off and travel to the heart or lungs, causing a medical emergency.

A thrombus is a blood clot that occurs in one of your veins. A thrombus does not move and partially or entirely stops the flow of blood through that vein.

Your arteries allow oxygen within your blood to flow from your heart to your body. Arteries deliver oxygen via blood to all of your tissues and organs. 

Your veins do the opposite. They carry blood back to your lungs to trade carbon dioxide for more oxygen. Every cell in your body requires this steady supply of oxygen-rich blood to stay alive. 

Clotting is an important process in which blood thickens and creates a scab. This stops the bleeding from an injury. When this coagulation happens inside of your circulatory system, it can cause problems. 

If a clot forms within your artery or vein, or breaks off and travels to the heart or lungs, you will have a medical emergency. This is because the clot blocks the flow of blood to or from your heart. Your brain and body do not receive enough oxygen when this happens. 

Symptoms of blood clots and a thrombus

When a clot forms in one of your veins and does not move, it is called a thrombus. A thrombus is more likely to form in your veins than in your arteries. This is because the overall pressure of the blood flow through your veins is lower. 

Arteries are more likely to develop hardening, also known as atherosclerosis. The higher pressure and speed of blood flow in your arteries makes a thrombus or blood clot less likely to form there.

Symptoms of a thrombus include:

  • Pain or discomfort
  • Heaviness or tenderness in the affected area
  • Swelling, itchiness, or warmth near the clot
  • Skin changes such as discoloration or thickening

Causes of blood clots and a thrombus

A thrombus is most likely to form in your legs or arms. They can occasionally occur in your pelvis or core. 

A thrombus can be caused by a variety of factors, including:

  • Disease or injury to leg veins
  • Immobility or not being able to move around 
  • A broken bone
  • Certain medications
  • Obesity
  • Autoimmune disorders

Other risk factors for developing a thrombus include:

Diagnosis for a thrombus

Only a licensed healthcare professional can diagnose a thrombus. There are a few ways that your doctor will determine whether you are experiencing a thrombus. 

First, you will likely undergo duplex ultrasonography, which is an imaging test that uses sound waves to look at the flow of blood in your veins. Your doctor will look for any blockages that may be caused by a thrombus.

An alternative to duplex ultrasonography is a procedure called contrast venography. 

In this procedure, your doctor injects your vein with a special highly-visible liquid and then takes an X-ray to locate any blockages. This is the most effective way to locate a thrombus. Since it is invasive and has more risks for infection, most doctors prefer to rely on duplex ultrasonography exams.

Finally, your doctor may perform a blood test called a D-dimer that looks for the enzymes present after a blood clot starts to break up. If your test is negative, you probably do not have a thrombus or blood clot.

Treatments for a thrombus

The treatment for this blood clot that is stationary in one of your veins is a type of medication known as a blood-thinner. 

The blood-thinners that are most often administered to treat a thrombus are heparin and warfarin.

Blood clots can also be prevented by:

  • Wearing compression socks or sleeves 
  • Moving as often as possible
  • Eating a healthy diet
  • Engaging in regular exercise

Possible complications and side effects

The possible complications from a thrombus or blood clot are very serious. 

If the clot breaks away and travels to your lungs, it can cause a pulmonary embolism

If the clot reaches your heart, it can cause a heart attack. 

If it travels to your brain, it can cause a stroke.

In order to avoid these serious and potentially lethal complications, it is important to seek medical care immediately if you think you have a blood clot or thrombus. 

Quick intervention can make all the difference and be life-saving in this situation. 


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American Association for Clinical Chemistry: "D-dimer."

American Society of Hematology: "Blood Clots."

Centers for Disease Control and Prevention: "Diagnosis and Treatment of Venous Thromboembolism."

Harvard Health Publishing: "How to Prevent Clots in the Legs and Lungs."

Johns Hopkins Medicine: "Thrombosis."

National Blood Clot Alliance: "SIGNS AND SYMPTOMS OF BLOOD CLOTS."

National Blood Clot Alliance: "TREATMENT OF THROMBOSIS."

North American Thrombosis Forum: "What is Thrombosis?"

St. Luke's Hospital: "Complications of Deep Vein Thrombosis."

UNC Hemophilia and Thrombosis Center: "What is a blood clot?"