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About 1 in 10 people with cancer will develop a blood clot at some point. Blood clots are also the second leading cause of death in people with cancer. It’s important to understand what increases your risk for blood clots, what the signs and symptoms are, and ways to prevent them.
Blood clots are gel-like masses that form when blood clumps together?. When we are hurt or bleeding, coagulation triggers blood cells called platelets and other substances to the area to form a blood clot. This helps stop bleeding. Normally, your body will dissolve the blood clot.
Some blood clots form even when you aren't injured.
Both thrombi and emboli can block blood flow, causing a thrombosis or embolism. The problems caused depend on where the clot is.
Blood clots can be described by which blood vessel they’re in (vein or artery) and how deep in the body they are.
Venous (vein) blood clots include:
An arterial thrombosis is a blood clot that happens in an artery instead of a vein. These are less common but also very serious.
Blood clots are often called different names depending on which organ they affect:
People with cancer have a higher risk of developing blood clots. But certain cancers ( pancreas, stomach, lung, colon or rectum, kidney, or multiple myeloma) are more likely to cause blood clots than others.
The stage and grade of cancer also affects the risk of blood clots. People with metastatic cancer (stage 3 or 4) and high-grade cancers have a higher risk for blood clots.
Cancer treatments and medicines that can increase your risk for blood clots:
Certain non-cancer health conditions can increase a person’s risk of developing a blood clot. Some of the most common ones are:
The more risk factors you have, the higher the chance of developing a blood clot. Your risk goes up even more after age 65.
If you have a higher risk of having a blood clot and are starting cancer treatment, your doctor might talk to you about taking medicine to prevent them.
The types of medicines most often used to prevent blood clots are anticoagulants and antiplatelets. Some common ones are aspirin, warfarin, and heparin. Your doctor also might suggest medicine to prevent blood clots during certain times when your risk is higher such as when traveling, after surgery, or during a hospital stay.
IVC filter. An IVC filter is a special medical device placed into the inferior vena cava (IVC), a large vein below the heart. IVC filters stop blood clots from traveling to the lungs and causing a pulmonary embolism (PE).
Compression devices. If you’re in the hospital, you might be asked to wear compression devices on your lower legs or feet to prevent blood clots. These inflate and deflate with air to improve blood flow. Compression stockings might also be used.
Blood clots don’t always cause symptoms. If you are at risk for a blood clot, you should know the most common signs and symptoms. The signs and symptoms of a blood clot depend on where it is in the body.
?Some blood clots can be life-threatening. Get medical help immediately if you think you might have a blood clot.
If your doctor thinks you have a blood clot, they will order certain tests that can help confirm it:
Some blood clots are treated with the same medicines used to prevent them. These medicines don’t get rid of a clot that’s already there. But they prevent clots from growing and new ones from forming. The body naturally breaks down blood clots over time.
Medicines used to break down a clot are called thrombolytics or fibrinolytics. These medicines are usually only used for large, life-threatening blood clots such as strokes, heart attacks, and some pulmonary emboli. These medicines can have severe side effects, like heavy bleeding that won’t stop, so are only used in certain situations.
Any medicine that affects the blood has risks. Talk to your doctor about what the possible risks and benefits are for you. You might have to decide if the risk of having a blood clot is higher than the risk of bleeding from medicines that prevent blood clots. You and your doctor should make this decision together after you’ve talked about all the risks and benefits.
Some people might need to have a blood clot removed if they can’t take blood thinners. A thrombectomy or embolectomy is a procedure that removes a blood clot that is causing major problems.
There are some things you can do on your own to help lower your risk of developing a blood clot:
Ask your cancer care team:
If you are being treated for a blood clot, you might want to ask:
Talk to your cancer care team if you take medicines or supplements that can affect how your blood clots. They might suggest you avoid them while you’re being treated for a blood clot. Some common ones are:
If you are taking medicine to prevent or to treat a blood clot, take care to not injure yourself. Even minor injuries can make you bleed more than you usually would. Learn more about how to protect yourself if you are at risk for bleeding.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as editors and translators with extensive experience in medical writing.
Bauer KA. Anticoagulation therapy for venous thromboembolism in adult patients with malignancy. UpToDate. UpToDate; 2023. Updated September 2023. Accessed December 1, 2023. https://www.uptodate.com/contents/anticoagulation-therapy-for-venous-thromboembolism-lower-extremity-venous-thrombosis-and-pulmonary-embolism-in-adult-patients-with-malignancy?
Bauer KA. Risk and prevention of venous thromboembolism in adults with cancer. UpToDate. UpToDate; 2023. Updated September 2023. Accessed December 1, 2023. https://www.uptodate.com/contents/risk-and-prevention-of-venous-thromboembolism-in-adults-with-cancer?
Chisakul T. Cancer-associated hypercoagulable state: causes and mechanisms. UpToDate. UpToDate; 2023. Updated October 2022. Accessed December 1, 2023. https://www.uptodate.com/contents/cancer-associated-hypercoagulable-state-causes-and-mechanisms?
Falanga A, Leader A, Ambaglio C, Bagoly Z, Castaman G, Elalamy I, Lecumberri R, Niessner A, Pabinger I, Szmit S, Trinchero A, Ten Cate H, Rocca B. EHA guidelines on management of antithrombotic treatments in thrombocytopenic patients with cancer. Hemasphere. 2022;6(8):e750. doi: 10.1097/HS9.0000000000000750. PMID: 35924068; PMCID: PMC9281983.
Lip GYH. Venous thromboembolism: initiation of anticoagulation. UpToDate. UpToDate; 2023. Updated March 2023. Accessed December 1, 2023. https://www.uptodate.com/contents/venous-thromboembolism-initiation-of-anticoagulation?
National Comprehensive Care Network. Blood clots and cancer. NCCN Guidelines for Patients. Updated 2023. Accessed December 1, 2023. https://www.nccn.org/patients/guidelines/content/PDF/bloodclots-patient.pdf
National Comprehensive Care Network. Cancer-associated venous thromboembolic disease. Version 2.2023. NCCN Guidelines. Updated June 2023. Accessed December 1, 2023. https://www.nccn.org/professionals/physician_gls/pdf/vte.pdf
Last Revised: February 6, 2024
American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.
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