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.