Cancer, Chemotherapy and Warfarin

By: Alere Staff

Cancer, and the chemotherapy treatment associated with various cancers, increases your risk of developing a blood clot. While blood clots are normal for repairing an injury, blood clots within the vein can be very dangerous. Arteries, Veins and Capillaries are all types of blood vessels or ‘tubes’ that carry blood through the body. Commonly found toward the end of our arms and legs, veins carry blood back to the heart. Veins are the most common site for a blood clot to cause problems in your venous circulation. It is important that patients with cancer and undergoing chemotherapy reduce their risk of developing a clot.

Deep Vein Thrombosis and Cancer

It is normal for doctors who discover a blood clot in an otherwise healthy person to also look for an undiagnosed cancer. While simple deep vein thrombosis (DVT) is fairly common and has many causes, cancer can also be causing a DVT and may have been previously undetected. Since cancer is best treated by catching it early, your physician may determine that additional tests are necessary to determine if an undiagnosed cancer is a factor.

Being diagnosed with cancer can increase one’s risk of developing a blood clot in the venous circulation by four times. While undergoing chemotherapy, your risk of developing a blood clot in a small vein increases by as much as six and a half times.

Protection may be provided to you to reduce your risk of blood clots in medicinal form. Some patients will be given an injectable drug called a low molecular weight heparin (LMWH) while others may receive a drug called warfarin (or brand of warfarin such as Coumadin®). These treatments may continue until the risk of blood clot development has lowered.

If warfarin has been selected for you, it is important you keep to your blood test schedule. A simple check of your blood at regular intervals will considerably lessen your risk of these complications while protecting your blood from forming unwanted clots.


1.  Toth, J. Anticoagulation Management in Patients with Cancer. US Pharm.2008;33(7)(Oncology suppl):23-26.

COUMADIN® is a registered trademark of Bristol-Myers Squibb Pharma Company. Alere is not affiliated or associated with Bristol-Myers Squibb Pharma Company or the COUMADIN® trademark.