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Deep vein thrombosis


Deep vein thrombosis (DVT) is a condition in which a blood clot forms in one of your deep veins, usually in your leg. DVT can cause pain and swelling and may lead to serious complications so it’s best to be aware of the symptoms and know how you can prevent it.

About DVT 

DVT happens when a blood clot forms in a deep vein.

DVT is most common in the deep veins of your lower leg (calf). They can spread up to the veins in your thigh and they can also first develop there. Deep veins in your leg pass through the centre of the leg and are surrounded by a layer of muscle (see diagram).

More rarely, DVTs can develop in other deep veins such as the ones in your arm.

a blood clot in the deep vein of the calf which causes deep vein thrombosis

When blood clots form in the superficial veins, which lie just under your skin, the condition is known as superficial thrombophlebitis. These superficial blood clots are different to DVT and are less serious.

Symptoms of DVT  

Many of the blood clots that cause DVT are small and don't produce any symptoms. Your body will usually be able to gradually break them down with no long-term effects.

Larger clots can partly or completely block the blood flow in your vein and cause symptoms such as:

  • swelling of the affected leg
  • pain and tenderness in the affected leg – you may also find it difficult to stand properly with your full weight on the affected leg
  • a change in the colour of your skin; for example, redness
  • skin that feels warm or hot to the touch. Although not necessarily a result of DVT, if you have these symptoms you should visit your GP.

Complications of DVT 

DVT may not cause you any further problems, but possible complications can include the following.

Pulmonary embolism

This is the most serious complication of DVT. A pulmonary embolism (PE) happens when a piece of the blood clot from a DVT breaks off and travels through your bloodstream to your lungs, where it blocks one of the blood vessels in your lungs. This is serious and in severe cases, can be fatal. In Australia, over half of the 14,716 cases of DVT reported in 2008 developed PE and about one-third died. Together, DVT and PE are the fifth leading cause of death in Australia, causing more deaths than either breast cancer or prostate cancer.

Post-thrombotic syndrome

This happens if DVT damages the valves in your deep veins, so that instead of flowing upwards, the blood pools in your lower leg. This can eventually lead to long-term pain, swelling and, in severe cases, ulcers on your leg.

Limb ischaemia

This is a rare complication that only happens in a very extensive DVT. Because of the blood clot, the pressure in your vein can become very high. This can block the flow of blood through your arteries, so less oxygen is carried to the affected leg. This can be painful and lead to skin ulcers, infection and even gangrene.

Causes of DVT  

You are more likely to get a DVT if you:

  • are over 40
  • are immobile, for example, if you have had an operation (especially on a hip or knee) or are travelling for long distances and so are not able to move your legs
  • have had a blood clot in a vein before
  • have a family history of blood clots in veins
  • have a condition causing your blood to clot more easily (this is called thrombophilia)
  • are very overweight (obese)
  • have cancer or have had cancer treatment
  • have heart disease or circulation problems
  • are a woman taking a contraception pill that contains oestrogen, or hormone replacement therapy (HRT)
  • are pregnant or have recently had a baby.

Travel risks

There is evidence that long-haul flights (lasting over four hours or over 4000 km) can increase your risk of developing DVT. The risk is mainly the result of sitting down for long periods of time, which can happen during any form of long-distance travel, whether by car, bus, train or air.

It's difficult to say whether the travelling itself directly causes DVT, or whether people who get DVT after travelling are at risk for other reasons. Generally, your risk of developing DVT when travelling is very small – about one DVT episode in every 4500 flights lasting over four hours – unless you have at least one of the other risk factors mentioned above (such as a history of DVT or cancer). If this is the case, you should talk to your GP before you fly.

Diagnosis of DVT 

Your GP will ask about your symptoms and examine you. If he or she thinks that you might have a DVT, you may be referred to a specialist. You may have the following tests in hospital.

  • A blood test called a D-Dimer. This measures a substance that develops when a blood clot breaks down. If this is negative, it's unlikely that you have a DVT.
  • A Doppler ultrasound. This is a test that uses sound waves to look at your blood as it flows through your blood vessels. It's the best test to detect blood clots above your knee.
  • A venogram. In this test, a special dye is injected into your vein, which shows up the vein on X-ray. This is the best way of showing clots below your knee.

Treatment of DVT 


Anticoagulant medicines are the standard treatment for DVT. They change chemicals in your blood to stop clots forming so easily and old ones from getting any bigger. They can't dissolve clots that you already have – your body will do that itself over time. Anticoagulants include heparin and warfarin.

Thrombolytic medicines are medicines that work by dissolving blood clots; but they are more likely to cause bleeding and so are rarely used to treat DVT.

Compression stockings

These are also called graduated compression stockings. Your doctor may ask you to wear these to ease your pain and reduce swelling, and to prevent post-thrombotic syndrome. You may need to wear them from 3 months to two years or even more after having a DVT.

Prevention of DVT 

Ask your GP for advice if you think you're at risk of developing a DVT.

There are a number of things you may be able to do to reduce your risk, such as stopping smoking if you smoke, or losing weight if you're overweight. Regular walking can help to improve the blood circulation in your legs and help to prevent another DVT from developing.

There is no good evidence that taking aspirin on its own reduces your risk of developing DVT.

If you're having surgery

Surgery and some medical treatments can increase your risk of developing DVT. So, if you're going to hospital for an operation, you will usually have an assessment to check your risk of developing DVT before you have your operation. There are many things that can be done to keep your risk of developing DVT during surgery as low as possible. You may be given anticoagulant medicines before and after surgery, or be asked to wear compression stockings. You may also be given a mechanical pump to use on your feet and legs in the first few days after the operation. This is called an intermittent compression device. The pump automatically squeezes your feet and lower legs to help your blood circulate.

If you're travelling

  • Although it's unlikely that you will develop DVT when you're travelling, there are some steps you can take to reduce your chances of developing a blood clot. Take short walks – if you're a passenger, walk up and down the aisle of the coach, train or plane. Exercise the muscles of your lower legs, which act as a pump for the blood in your veins – regularly bend and straighten your toes, ankles and legs.
  • Wear loose-fitting clothes.
  • Keep hydrated by making sure you drink enough water.
  • Don't drink too much alcohol or too many drinks that contain caffeine, such as coffee.
  • Don't take sleeping tablets, as these will stop you keeping your legs active.
  • Wear compression stockings if you have other risk factors for DVT.

If your GP has told you that you're at high risk for DVT (for example, if you have a previous history of DVT or a blood clotting disorder), you may need heparin injections and specially fitted compression stocking as well. Talk to your GP or haematologist for more information.

If you develop swelling or pain in your calf or thigh, or if you have breathing problems or chest pain after travelling, seek urgent medical attention.

Further information 


Heart Foundation of Australia


Access Economics, on behalf of The Australia and New Zealand Working Party on the Management and Prevention of Venous Thromboembolism. The burden of venous thromboembolism in Australia. 2008.

Alexander M Fawcett J Runciman P. Nursing Practice: Hospital and Home - The Adult. 3rd ed. London: Churchill Livingstone. 2006: 910–911.

The Australia and New Zealand Working Party on the Management and Prevention of Venous Thromboembolism. Prevention of venous thromboembolism. Best practice guidelines for Australia and New Zealand. 4th ed. [online] [accessed 25 Jul 2011] Available from:

Better Health Channel, Victorian Government. Deep vein thrombosis. [online] c2010. [Accessed 25 Jul 2011] Available from:

British Committee for Standards in Haematology Task Force. The diagnosis of deep vein thrombosis in symptomatic outpatients and the potential for clinical assessment and D-dimer assays to reduce the need for diagnostic imaging. Br J of Haematol. 2004; 124:15-25.

Chapman NH Brighton T Harris MF et al. Venous thromboembolism – Management in general practice. Australian Family Physician. 2009; 38: 36–40.

Clinical Knowledge Summaries. Deep vein thrombosis. [online] London: National Institutes for Health and Clinical Excellence. 2008 [last updated Mar 2009, accessed 25 Jul 2011] Available from:

Firkin F Nandurkar H. Flying and thromboembolism. Aust Prescr. 2009; 32: 148–150.

Khoon Ho W. Deep vein thrombosis: risks and diagnosis. Australian Family Physician. 2010; 39: 468–474.

Longmore M Wilkinson I Turmezei T et al. Oxford handbook of clinical medicine. 7th ed. Oxford: Oxford University Press, 2007: 596.

McManus RJ Fitzmaurice DA Murray E Taylor C. Thromboembolism. BMJ Clinical Evidence. 2010.

myDr. Deep vein thrombosis. [online] St Leonards, NSW: UBM Medica Australia. 2007 [Accessed on 25 Jul 2011]. Available from:

National Heart Foundation of Australia. Cardiovascular conditions: deep vein thrombosis. [online] Australia: National Heart Foundation of Australia [accessed 25 Jul 2011] Available from:

National Health and Medical Research Council. Clinical Practice guideline for the prevention of venous thromboembolism in patients admitted to Australian hospitals. [online] Canberra, ACT: Commonwealth of Australia. 2010 [Accessed 25 Jul 2011] Available from:

National Institute for Health and Clinical Excellence (NICE). Venous thromboembolism – reducing the risk of thromboembolism (DVT and pulmonary embolism) in in-patients undergoing surgery. [online] Apr 2007. Available from:

National Institute for Health and Clinical Excellence (NICE). Venous thromboembolism – reducing the risk of thromboembolism (DVT and pulmonary embolism) in in-patients undergoing surgery. [online] Apr 2007. Available from:

Pharmacy Self Care. Deep vein thrombosis. Deakin, ACT: Pharmaceutical Society of Australia. 2010.

Scottish Intercollegiate Guidelines Network (SIGN). Prophylaxis of venous thromboembolism. [online] Edinburgh, Scotland: SIGN. Oct 2002. Available from:

Scurr JH Machin SJ Bailey-King S et al. Frequency and prevention of symptomless deep-vein thrombosis in long-haul flights: a randomised trial. Lancet. 2001; 357: 1485-89.

Simon C Everitt H Kendrick T. Oxford handbook of general practice. 2nd ed. Oxford: Oxford University Press, 2007.

Wilson E. Preventing deaths from VTE in hospital 1: Risk factors. Nurs Times. 103; (37): 26.

World Health Organisation (WHO). WHO Research into global hazards of travel (WRIGHT) project. [accessed 23 Jan 2009 ] Available from:

Last published: 31 January 2012

This information has been developed and reviewed for Bupa by health professionals. To the best of their knowledge it is current and based on reputable sources of medical research. It should be used as a guide only and should not be relied upon as a substitute for professional medical or other health professional advice.

Bupa Australia Pty Ltd makes no warranties or representations regarding the completeness or accuracy of the information. Bupa Australia is not liable for any loss or damage you suffer arising out of the use of or reliance on the information. Except that which cannot be excluded by law. We recommend that you consult your doctor or other qualified health professional if you have questions or concerns about your health. For more details on how we produce our health content, visit the About our health information page.

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