It’s normal for your blood to clot so it can stop the bleeding if one of your blood vessels is injured. However, blood clots can form in or travel to the blood vessels in your brain, heart, kidneys, lungs and limbs. If they get stuck there, they cause problems, sometimes life-threatening ones.
There are things you can do to reduce your chance of getting a blood clot, including taking anticoagulants or antiplatelets if your risk is high.2 Blood clots can be treated if found early enough, including with blood thinners and other medication.
Problems caused by blood clots
A blood clot (thrombus) can develop in your veins, which carry blood to your heart, or your arteries, which carry blood away from your heart.
- A blood clot in one of the veins deep in your legs is called a deep vein thrombosis (DVT).
- If a blood clot in a deep vein breaks off and travels through your bloodstream to your lungs and blocks the blood flow there, it causes a pulmonary embolism.
- A blood clot can also form when the lining in your arteries has thickened making it harder for the blood to flow through. This can cause a heart attack, stroke, or transient ischaemic attack (TIA).
What causes blood clots?
Some conditions, such as genetic disorders3 and diabetes4 can make your blood clot too much or not dissolve properly.
Smoking can also increase the risk of blood clotting in women taking oral contraceptives (the pill).5
Most DVT is caused by not moving much, so it develops most often when you are in hospital, and less often, if you fly on a long-haul flight. Find out more about the cause of DVT.
Pulmonary embolism most often occurs when a blood clot in your leg travels to your lungs. Find out more about the cause of pulmonary embolism.
Arterial clots that lead to heart attacks, strokes and TIAs are caused by fatty deposits building up along the walls of your arteries over time, narrowing them and making it harder for blood to flow through them. This is called coronary heart disease.
Am I at risk for a blood clot?
The following factors increase your risk of developing a blood clot:
- Hospitalisation for illness or surgery.
- Major surgery, particularly of the pelvis, abdomen, hip, knee.
- Severe trauma, such as a car accident.
- Injury to a vein that may have been caused by a broken bone or severe muscle injury.
- Hip or knee replacement surgery.
- Cancer and cancer treatments.
- Use of birth control methods that contain oestrogen, such as the pill, patch or ring.
- Pregnancy, which includes the six weeks after the baby is born.
- The use of hormone replacement therapy, which contains oestrogen.
- A family history of blood clots.
- Confinement to bed.
- Sitting too long, especially with legs crossed.
What are the symptoms of blood clots?
How do blood clots get diagnosed?
What is the treatment for blood clots?
There are different treatments depending on what type of blood clot you have.
You may be prescribed an anticoagulant to thin your blood, or another medication to dissolve the clot. You may need surgery to remove the clot, or to widen your artery or bypass the clocked artery.
What self-care can I do if I have blood clots?
If you have a DVT, wear your compression stockings as advised by your doctor, and do DVT prevention exercises (see video in Resources).
With any type of clot, take your medication.
If you have a clot in your arteries, then follow the dietary advice of your doctor. See coronary heart disease for more information.
What support is there for living with blood clots?
What can I do to prevent blood clots?
You can reduce your risk of clots in your arteries (arterial thrombosis) if you:
- stop smoking
- exercise each day
- eating heart healthy foods
- lose weight if you are overweight or obese
- drink less alcohol.
If you're at a high risk of getting a blood clot in your arteries, your doctor may recommend medication to reduce your cholesterol, blood pressure or risk of your blood clotting.
If you are travelling or in hospital, reduce the risk of DVT by wearing compression stockings, moving your feet and legs as much as possible and drinking plenty of water.
- Acute on Chronic Kidney Disease. Patient Info, UK, 2012
- An update on antithrombotic medicines - What does primary care need to know? Best Practice Journal, NZ, 2015
- Inherited Causes of Blood Clots Indiana Hemophilia and Thrombosis Center, USA, 2017
- Smoking prevention and cessation in adolescents: Changing futures, saving lives. Best Practice Journal, NZ, 2013