Warfarin and Vitamin K - Topic Overview
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.
- Vitamin K normally helps your blood clot so wounds don't bleed too much.
- Warfarin works against vitamin K, making your blood clot more slowly.
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.
How to get a steady amount of vitamin K
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.
Check with your doctor before you make big changes in what you eat, such as starting a diet to lose weight.
Adding vitamin K
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.
Vitamin K content of select foods1
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. If you already take a product that contains vitamin K, do not stop taking it without talking with your doctor first.