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The Effects of Broccoli & Warfarin

author image Adam Cloe Ph.D./M.D.
Adam Cloe has been published in various scientific journals, including the "Journal of Biochemistry." He is currently a pathology resident at the University of Chicago. Cloe holds a Bachelor of Arts in biochemistry from Boston University, a M.D. from the University of Chicago and a Ph.D. in pathology from the University of Chicago.
The Effects of Broccoli & Warfarin
A elderly couple eat broccoli for dinner. Photo Credit: XiXinXing/iStock/Getty Images

Warfarin is a medication doctors commonly prescribe to help prevent blood clotting. The effectiveness of warfarin hinges on its effects on vitamin K levels. Increasing the amount of vitamin K in your diet by eating more broccoli can make the warfarin less effective, so talk to your doctor before making any changes to your diet while on warfarin.

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About Warfarin

Warfarin, sold under the brand name Coumadin, is a prescription blood thinner. Doctors prescribe this medication for patients who have an increased risk of developing blood clots. Blood clots can develop in your veins and other parts of your cardiovascular system and restrict blood flow. Sometimes these clots can get into your lungs, resulting in a serious medical condition known as a pulmonary embolism. Taking warfarin makes it harder for your blood to clot, reducing your risk of developing pathologic blood clots.

Warfarin and Vitamin K

To understand how broccoli interacts with warfarin, you need to understand the relationship between warfarin and vitamin K. Vitamin K is needed for the chemical reactions that make blood clot. Warfarin works by blocking the effects of vitamin K, so it is harder for your blood to clot efficiently. As a result, changes in the amount of vitamin K you consume while on warfarin can affect how the drug works.

Broccoli and Vitamin K

Vitamin K is primarily found in green leafy vegetables, including broccoli. According to an article published in a 2005 issue of the "Journal of Food Composition and Analysis," 100 grams of broccoli contains approximately 100 micrograms of vitamin K, though the amount of the vitamin can vary depending on the type of broccoli and how it is prepared. This means broccoli is relatively high in vitamin K.


If you are on warfarin, the most important thing you can do is to eat a consistent amount of vitamin K each day, as your warfarin dosage will be tailored to thin your blood. Eating a large amount of broccoli when you normally don't may make the warfarin less effective, but you do not need to eliminate broccoli and other foods high in vitamin K. Talk to your doctor before making any changes to your diet.

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