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Warfarin is a pill that you take regularly to help prevent blood clots or to keep a clot from getting bigger. Coumadin is the common brand name for warfarin.
To ensure that warfarin is effectively thinning your blood, it's important to eat about the same amount of vitamin K every day.
So warfarin and vitamin K work against each other in your body. That is why, when you take warfarin, it's important that you not suddenly eat a lot more or a lot less vitamin K-rich food than you usually do.
It's up to you how much vitamin K you choose to eat. For example, if you already eat a lot of leafy green vegetables, that's fine. Just keep it about the same amount each day.
And if you take a multivitamin that contains vitamin K, be sure you take it every day.
If you want to start eating more of a food that's rich in vitamin K, talk to your doctor about how to add it safely. Your warfarin dose may need to be adjusted.
Use this list to get an idea of what foods are sources of vitamin K.
Food (no salt added)
Vitamin K (mcg)
Kale, boiled, drained
Spinach, frozen, boiled, drained
Spinach, boiled, drained
Collards, boiled, drained
Broccoli, boiled, drained
Brussels sprouts, boiled, drained
Cabbage, boiled, drained
Spinach egg noodles, cooked, enriched
Lettuce, green leaf, raw
Coleslaw, fast food
Okra, boiled, drained
Green peas, canned, drained
Lettuce (such as romaine), raw
Vegetables, mixed, frozen, boiled, drained
Lettuce, butterhead (such as Boston or Bibb), raw
Blueberries, frozen, sweetened
Peas, edible pods, boiled
Green peas, frozen, boiled
Tuna fish, light, in oil, drained
Lettuce, iceberg, raw
Soy beans (edamame), boiled
Scallion or spring onion, raw
Asparagus, boiled, drained
Marinara sauce for pasta, ready-to-serve
Cucumber, with peel, raw
Pistachios, dry roasted, salt added
1 oz (47 nuts)
Tea, brewed, prepared with tap water
6 fl oz
Green and black tea leaves do contain vitamin K before they are steeped in water, but a small serving of the hot tea itself does not.
Check with your doctor before you take any supplements or herbal products. Some of these may contain vitamin K.
To find out how well warfarin is working, you will get blood tests to measure how long it takes for your blood to clot. Your lab results are called your Prothrombin Time (PT) and International Normalized Ratio (INR) values. You may just hear about your INR.
Your INR needs to be in a safe range—not too high and not too low. Vitamin K can change how warfarin works, which changes your INR.
Keeping your warfarin and vitamin K intake steady every day helps keep you in a safe INR range.
Agricultural Research Service (2010). USDA National Nutrient Database for Standard Reference, Release 23. Available online: http://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/SR23/nutrlist/sr23w430.pdf.
Other Works Consulted
Agency for Healthcare Research and Quality (2010). Blood Thinner Pills: Your Guide to Using Them Safely (AHRQ Publication No. 09-0086-C). Rockville, MD: Agency for Healthcare Research and Quality. Available online: http://www.ahrq.gov/consumer/btpills.htm.
January 3, 2013
E. Gregory Thompson, MD - Internal Medicine & Rakesh K. Pai, MD, FACC - Cardiology, Electrophysiology
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