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Are You at Risk for a Blood Clot?

Your Health / Conditions / Blood Clots / Are You at Risk for a Blood Clot?​​​​​​​

Published on Nov 22, 2017
Medically reviewed by George H. Sands, MD, FAAN, FAHA


Venous thromboembolism (VTE) is a condition used to describe two related conditions, which involve blood clots, most often called deep vein thrombosis (DVT) and pulmonary embolism (PE). It’s easy enough to understand, right? Let’s break down the words. “Venous” means “in the veins,” and “thrombus” is the word for a non-moving “blood clot”. An “embolus” is an abnormal particle such as a clot or air bubble that moves around the body via your blood stream. When an embolus blocks blood flow in a blood vessel it is called an “embolism”.

Simply speaking, DVT is when a blood clot forms in a deep vein usually in the thigh or lower leg, and a PE is when a part of the clot breaks off in the veins and travel to the lungs. It’s important to understand these conditions because DVT/PE can be a serious life-threatening condition that can happen to anyone.

What’s So Important about Blood Clots?

When blood clots that form in the leg or thigh become loose and travel to the lungs, they can block blood flow causing serious problems or even death.

DVT and PE affect many people worldwide. In fact, there are around 50,000 VTE events across Australia and New Zealand every year. That's similar to the number of strokes that occur each year. It is predicted that the number of DVT and PE will continue to increase and by the year 2050, the number of Australasians affected will be approaching 100,000.

If you have a thrombus (or blood clot), your doctor will start treatment quickly to reduce the chances of it traveling in the blood stream and blocking blood flow to an artery in the lungs. Treatment may also reduce the chances of the blood clot happening again. DVTs are usually treated with medicines that are commonly called blood thinners. Less often, other treatments for DVTs including surgery or medicines called thrombolytics that break the clot up may be used. Treatment for PE requires either thrombolytics or surgery in addition to blood thinners.

Why Do Blood Clots Happen?

Three main categories of factors that lead to an increased risk for blood clots are known in the medical community as Virchow’s Triad, named after a Prussian doctor who worked in this area. The factors are:

  • Blood stasis: This is when the blood flow slows down or pools. This can happen for a number of reasons including immobility for prolonged periods, certain types of surgery, or chronic heart disease
  • ​​​​​​​Hypercoagulability: This state occurs when the blood coagulates, or sticks together more easily than normal. It may happen because of specific genetic causes, cancer, smoking, oral contraceptive use, and pregnancy among others
  • ​​​​​​​Vascular injury: This is injury or trauma to the walls of the veins. Injuries may occur, from things like surgery, bone fractures, placement of a venous catheter,or injection drug use

Risk Factors

As you might imagine, DVT and PE may occur in patients who may have a combination of the factors listed above in Virchow’s triad. Some conditions putting people at a higher risk for these blood clots are if they have:

  • Had knee or hip surgery
  • Had trauma and/or bone fractures
  • Had knee or hip surgery
  • An age older than 40 years
  • Been on prolonged bed rest
  • Suffered a serious medical illness, infection, heart attack, or stroke
  • Cancer
  • Cancer and are receiving chemotherapy
  • Had a previous DVT or PE

Symptoms and Signs

DVT may have no symptoms at all or may include different combinations of pain, tenderness, discolouration, and leg swelling (that leaves an indentation when pressed). PE may include symptoms of shortness of breath, coughing (with or without blood in the phlegm), chest pain, a fast pulse (>100 beats per minute), and a low-grade fever. If blood clots in the lung cause the blood in the heart to back up it may cause low blood pressure and shock. If you experience any of these signs or symptoms of DVT or PE, contact your health care professional right away.

Prompt treatment for DVT and PE can reduce the chance that another event will occur. It is important to discuss the treatment plan with your health care team and learn what to expect while on that treatment plan. It’s also important to stick with the plan you agreed upon and follow up with your health care team regularly.


If you haven’t had a DVT or PE, but think you may be at an increased risk due to the factors described above, there are some ways to reduce the risk of DVT and PE from occurring. Talk with your health care professional about your risks and for help to:

  • ​​​​​​​Stop smoking (if you smoke)
  • ​​​​​​​Lose weight – obesity is risk factor for VTE and can also enhance the risk of other risk factors for VTE
  • ​​​​​​​Get active – to help keep your blood moving

It is important to be aware of this condition for you and your loved ones to reduce the risk of blood clots, when possible. If you suspect a DVT or PE, seek medical attention quickly.

George H. Sands, M.D. is a Senior Medical Director at Pfizer.


  1. The Australia and New Zealand Working Party on the Prevention of Venus Thromboembolism. Accessed 1/2/2017.
  2. Deloitte Access Economics. The burden of venous thromboembolism in Australia. 2008.

Last reviewed 20/07/2020

​​​​​​​External Resources

-Better Health Channel – Deep vein thrombosis

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