Diagnosis for deep vein thrombosis (DVT) typically involves imaging tests. Following diagnosis, a doctor can advise on suitable treatments.

DVT occurs when blood clots form in deep veins. If these clots break off, they can travel to the lungs through the bloodstream, leading to a blockage known as a pulmonary embolism.

Collectively, doctors refer to pulmonary embolism and DVT as venous thromboembolism (VTE).

This article discusses how doctors diagnose DVT, when tests are necessary, and what happens after a diagnosis.

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Doctors may begin the evaluation of DVT by taking a medical history and performing a physical examination. If the initial assessment indicates potential DVT, they may request a series of tests to confirm the diagnosis or rule out other possible causes.

Duplex ultrasonography

Duplex ultrasonography, or duplex scan, is the standard imaging test for diagnosing DVT. It combines conventional ultrasound with Doppler ultrasound to use sound waves to examine blood flow in the veins.

Doctors may use this imaging method to examine a person’s legs for potential narrowing or blockages in deep veins.

D-dimer test

A D-dimer test can be the first step to look for signs of a blood clot. It measures a substance in the blood known as D-dimer that releases when fibrin, a protein that stops bleeding, dissolves.

While this test cannot confirm a diagnosis, it can help rule out DVT. Doctors may also use the test to monitor treatment and determine the risk of a future clot.

A doctor may also order other laboratory tests that evaluate a person’s coagulation status and oxygen levels in the blood. Low blood oxygen can also be a sign of a blood clot.

Learn more about D-dimer tests here.


Doctors use conventional ultrasonography to directly visualize the lining of the veins and identify thrombi (blood clots) and check for abnormal vein compressibility.

The test is more suitable for diagnosing femoral and popliteal vein thrombosis. It is less accurate for calf or iliac vein thrombosis.

Contrast venography

In contrast venography, or a venogram, doctors inject a contrast dye through a catheter into a large vein. This dye aids in visualizing the blood’s circulation through the vein, which a special type of X-ray captures.

It is the imaging gold standard for DVT, but doctors use it less frequently due to its invasive nature.

When doctors suspect DVT, they typically assess the probability and risk using the Wells scoring system. The tool helps determine when a subsequent investigation is necessary and is a crucial management decision a doctor makes.

People may also go to a doctor when they experience symptoms such as leg swelling. As DVT symptoms are nonspecific and tend to be similar to conditions such as cellulitis and muscle injury, a doctor may test for DVT to confirm or rule out the diagnosis.

A doctor may assess for DVT in the clinic or hospital. A person may get the necessary lab tests inside the facility or at a laboratory outside the health facilities.

Imaging tests such as duplex ultrasounds and venograms typically happen in hospital X-ray departments.

Prompt treatment for DVT is crucial because the blood clot can break loose and lead to complications such as pulmonary embolism.

Treatment usually includes medications to break clots and prevent them from forming. Common medications include anticoagulants and thrombolytic therapy.

In rare cases, a person may need to undergo surgery to remove the clot. Thrombectomy is the removal of the clot, while embolectomy involves the removal of the blockage in the lungs.

A person’s doctor can advise on which treatments they recommend and answer any questions.

Learn more about treatments for blood clots here.

It is essential for a person to go to the doctor right away or to the emergency room if they notice signs of DVT. These can include:

  • swelling of the leg along a vein in the leg
  • leg pain or tenderness, which may only appear when standing or walking
  • increased warmth in the swollen or painful area of the leg

Learn more about the symptoms of DVT here.

Experiencing the following may indicate pulmonary embolism, which can be fatal:

Learn more about pulmonary embolism here.

Here are some frequently asked questions about DVT.

What are the warning signs of deep vein thrombosis?

Warning signs of DVT include:

  • pain or tenderness in the thigh or calf
  • leg swelling
  • skin that feels warm to touch
  • red streaks or reddish discoloration

A person should seek medical advice if they experience these symptoms.

What is the first-line diagnosis for DVT?

Ultrasound, whether conventional or duplex, is the most common diagnostic test for DVT after a comprehensive physical examination and medical history.

How can I test for DVT at home?

It is not possible to test for DVT at home. As the condition can be serious, it is important to contact a doctor for a diagnosis if a person experiences symptoms of DVT.

Can a blood test detect DVT?

A blood test, such as a D-dimer test, does not diagnose DVT. However, it can suggest if a person has a blood clot or a blood clotting problem. This can help rule out DVT or other conditions.

Doctors typically use ultrasound to diagnose deep vein thrombosis (DVT). This can include conventional ultrasonography and duplex ultrasonography.

Other tests, such as the D-dimer test and contrast venography, may help to diagnose the condition.

It is best for a person to contact a doctor or seek medical advice if they experience symptoms of DVT. The condition can be serious, so it is important to receive an accurate diagnosis and begin treatment as early as possible.