Blood clots and cancer

Cancer or cancer treatment may increase your risk of blood clots. Your doctor or nurse will tell you about ways to prevent or treat blood clots.

Blood clots (thrombosis)

Cancer can increase your risk of developing a blood clot (thrombosis). Some cancer treatments may also increase this risk. 

Blood clots can be very serious if they are not treated. If you have a blood clot, you may need drugs to thin your blood. These can successfully treat blood clots. 

Blood clot symptoms

Symptoms of a blood clot depend on where it is in the body. A clot can form in:

  • the leg (usually in the calf) or arm – this may cause pain, swelling, heat and redness in the area. This is called a deep vein thrombosis (DVT).
  • the lungs – this may cause shortness of breath or chest pain. This type of blood clot is called a pulmonary embolism.
  • the brain – this may cause mild symptoms such as headaches, blurred vision, or dizziness. Blood clots in the brain can also cause a stroke or a transient ischaemic attack (TIA). Symptoms may include weakness, numbness or pins and needles, or problems with your speech or swallowing.
  • the heart – this may cause chest pain (angina). It can sometimes cause a heart attack.
  • the tummy area (abdomen) – this may cause pain in the abdomen and affect the bowel, liver or spleen.

It is important to tell your doctor or nurse straight away if you have any of these symptoms. If you cannot speak to a doctor, call 999 for an ambulance or go to A&E.

Are you at risk of blood clots?

If you have cancer, your risk of developing a blood clot may increase. The risk is higher:

  • with some types of cancer
  • with some cancer treatments
  • if the blood cells (platelets) or chemicals in your blood that control clotting are affected
  • if you sit still for long periods of time
  • after surgery.

Some medical conditions or lifestyle factors can also increase your risk of developing blood clots. The NHS has general information about blood clots.


Preventing blood clots during cancer treatment

There are things you can do to help lower your risk of blood clots. These include:

  • taking short walks regularly
  • exercising the muscles in your legs regularly, even when you are not walking around.
  • drinking plenty of water
  • taking deep breaths to keep your blood flowing.

If you are worried about your risk of blood clots, talk to your doctor or nurse. They can tell you about things that may reduce your risk.

If you are at risk, your doctor may prescribe medicines to stop blood clots forming.

Preventing blood clots after surgery

Your nurse may give you compression stockings to put on before surgery. You may also have to wear these for a short time afterwards. Compression stockings reduce the risk of getting a blood clot in your legs. 

You will be encouraged to get out of bed quite soon after your operation. Moving around will help you recover more quickly and help reduce the risk of blood clots. While you are in bed, it is important to move your legs regularly. Your nurse or physiotherapist can show you some exercises.

Your nurse may give you medicines to help prevent blood clots forming. These are called anti-coagulants. Usually you have these as an injection under the skin or sometimes as tablets.

Travel and blood clot risk

Travelling, especially flying, also increases the risk of developing a blood clot. You are particularly at risk if you sit still for long periods of time. This could happen when you are on a long-distance flight, or on long bus, train or car journeys.

You may also be more at risk if you have a personal or family history of blood clots.

Before you travel, ask your cancer doctor or specialist nurse about your risk of a blood clot.

They can tell you about anything you should do to reduce your risk while travelling – for example, they may give you advice about taking aspirin before a long flight.

Ask them if you should wear compression stockings for travel. These are below-the-knee stockings that keep gentle pressure on your legs and help blood flow. They are important if you are going on a flight of 4 hours or more.

Make sure your compression stockings are properly measured and fitted for you. You can ask your nurse or a pharmacist for advice.

Here are some other tips:

  • Book an aisle seat, especially on flights, to make it easier to move around.
  • Wear loose-fitting, comfortable clothing, especially around the waist and groin.
  • When sitting, exercise your legs, feet and toes about every 30 minutes.
  • Walk around when you can – try to walk up and down the aisles for a few minutes every hour.
  • Try some upper body and breathing exercises – these also help improve your circulation.
  • Avoid taking sleeping pills.
  • Drink plenty of water, especially during flights.
  • Avoid drinking too much alcohol or caffeine – these can dehydrate you.

Date reviewed

Reviewed: 01 December 2019
Next review: 01 November 2023

This content is currently being reviewed. New information will be coming soon.

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