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Blood clots

10-minute read

If you or someone else is having trouble breathing, or if you have symptoms of stroke or heart attack, call triple zero (000) and ask for an ambulance.

Key facts

  • Blood clotting can become a problem when it stops your blood from flowing properly.
  • A blood clot that forms in a blood vessel is called a thrombus.
  • Blood clots can cause different problems depending on where they are in your body.

What are blood clots?

Your blood is able to clot so that you don’t lose too much blood if you are injured. But blood clotting can become a problem when it stops blood flow through blood vessels.

Blood clots in blood vessels can be fatal if they aren’t treated. They can lead to problems such as a stroke, heart attack or pulmonary embolism.

If you think you may have a blood clot, see your doctor as soon as possible.

What are some types of blood clots and their symptoms?

Blood clots can cause different problems depending on where they are in your body.

Deep vein thrombosis (DVT)

A DVT is when a blood clot forms in one of the veins deep inside your body. DVTs mostly occur in your legs, but you can get a DVT anywhere in your body.

The most common symptoms of DVT are:

  • pain and swelling in the affected area, usually your calf or thigh
  • redness and a warm feeling around the area of the clot

Sometimes there are no symptoms.

Blood clot in the lungs

If a blood clot travels from a deep vein to your lungs, it’s called a pulmonary embolism.

Symptoms of pulmonary embolism include:

  • shortness of breath
  • chest pain
  • coughing up blood
  • sweating
  • rapid heartbeat
  • feeling dizzy

A major pulmonary embolism can be life-threatening.

If you think you may have a pulmonary embolism, go to the nearest emergency department or call triple zero (000) and ask for an ambulance.

Blood clot in the brain

A blood clot in your brain can cause a stroke.

Symptoms of a stroke can include:

  • weakness or drooping in the face, arm or leg
  • difficulty speaking or understanding
  • dizziness or loss of balance
  • blurred vision
  • difficulty swallowing

If you or someone else experiences signs of stroke, no matter how long they last, call triple zero (000) immediately and ask for an ambulance.

Blood clot in the heart

A blood clot in the blood vessels that supply your heart (coronary arteries) can lead to a heart attack.

Symptoms of a heart attack can include:

  • chest pain or discomfort (it may feel like your chest is being pressed or squeezed by a heavy object)
  • shortness of breath
  • feeling weak and light-headed
  • nausea
  • a cold sweat
  • feeling anxious
  • feeling dizzy or light-headed

If you have any of these symptoms, or if they get worse quickly or last longer than 10 minutes, call triple zero (000) and ask for an ambulance.

What causes blood clots?

A blood clot in a blood vessel (thrombus) can happen when:

  • Your blood starts to clot more easily.
  • There is damage to the wall of the blood vessel.
  • There are changes in how your blood flows. For example, blood flow in your legs can slow down if you sit or lie still for a long time.

Often, a combination of things leads to a blood clot.

What can increase the risk of blood clots?

You are more likely to develop a DVT if:

  • you’ve had recent surgery or an injury, especially a leg injury
  • you’ve had a blood clot before
  • you have a blood disorder or other condition that makes clotting more likely
  • you have a family history of blood clots
  • you smoke
  • you have an inflammatory condition
  • you stop moving around for a long period of time (for example, if you are on a long-haul flight)

Other factors that can increase your risk of a DVT include:

Having a problem with your blood vessels called atherosclerosis (a build-up of cholesterol and other material in the walls of your arteries) increases your risk of blood clots causing heart attack and stroke.

The AstraZeneca COVID-19 vaccine has been linked to a very rare blood-clotting disorder called thrombosis with thrombocytopenia syndrome (TTS). This vaccine is no longer available in Australia.

When should I see my doctor?

Blood clots can cause serious complications. So, see your doctor as soon as possible if you think you may have a blood clot.

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How are blood clots diagnosed?

If you think you may have a blood clot, it’s important to see a doctor right away. They will ask you about your symptoms and examine you.

Tests that can help diagnose a blood clot will depend on your symptoms and the part of your body that’s affected. Your doctor may recommend:

How are blood clots treated?

Treatment of a blood clot will depend on its location.

One treatment for blood clots is anticoagulant medicines (blood thinning medicines). These medicines stop blood clots from growing larger and prevent new clots from forming.

You may need to take this medicine for several months and see your doctor regularly to check that it’s working.

Sometimes blood clots are treated with a medicine or procedure to:

  • dissolve the clot
  • prevent the clot from breaking up and travelling to your lungs, heart or brain

If you have a DVT, compression stockings may help with your symptoms and improve the blood flow in your legs.

If you have a heart attack, stroke or pulmonary embolism, you will need to have emergency treatment in hospital.

Can blood clots be prevented?

Some conditions or activities can put you at increased risk of blood clots. Your doctor may recommend medicines or other treatments to reduce your risk of blood clots.

You can also help lower your risk by:

  • maintaining a healthy weight
  • getting enough physical activity
  • not smoking
  • avoiding hormonal contraception or hormone replacement therapy that contains oestrogen

Blood clot prevention when travelling

Long-distance travelling can increase your risk of getting a DVT. To reduce your risk of blood clots during long-distance travel, try these tips.

  • Get up and move about as much as possible.
  • Do foot exercises to help improve blood flow in your legs.
  • Drink plenty of fluids but avoid alcohol.

Ask your doctor about whether compression stockings are a good idea when travelling.

Lifestyle measures to help prevent heart attack and stroke

To reduce your risk of conditions such as heart attack and stroke, your doctor may recommend lifestyle measures. These can include:

Resources and support

Thrombosis Australia has more information on blood clots (thrombosis).

The Heart Foundation and Stroke Foundation have information on heart attack and stroke, including information in languages other than English.

If you want to know more about blood clots or need advice on what to do next, you can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: August 2023

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