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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)

Serving Size

Vitamin K (mcg)

Kale, boiled, drained

1 cup

1062

Spinach, frozen, boiled, drained

1 cup

1027

Spinach, boiled, drained

1 cup

889

Collards, boiled, drained

1 cup

836

Broccoli, boiled, drained

1 cup

220

Brussels sprouts, boiled, drained

1 cup

218

Parsley, raw

10 sprigs

164

Cabbage, boiled, drained

1 cup

163

Spinach egg noodles, cooked, enriched

1 cup

162

Spinach, raw

1 cup

145

Broccoli, raw

1 cup

89

Lettuce, green leaf, raw

1 cup

71

Coleslaw, fast food

¾ cup

70

Okra, boiled, drained

1 cup

64

Green peas, canned, drained

1 cup

63

Lettuce (such as romaine), raw

1 cup

57

Vegetables, mixed, frozen, boiled, drained

1 cup

43

Lettuce, butterhead (such as Boston or Bibb), raw

¼ head

42

Blueberries, frozen, sweetened

1 cup

41

Peas, edible pods, boiled

1 cup

40

Green peas, frozen, boiled

1 cup

38

Tuna fish, light, in oil, drained

3 oz

37

Celery, raw

1 cup

35

Lettuce, iceberg, raw

¼ head

33

Soy beans (edamame), boiled

1 cup

33

Kiwi, raw

1 medium

31

Scallion or spring onion, raw

1 medium

31

Asparagus, boiled, drained

4 spears

30

Blackberries, raw

1 cup

29

Blueberries, raw

1 cup

28

Marinara sauce for pasta, ready-to-serve

½ cup

18

Cucumber, with peel, raw

¼ large

12

Canola oil

1 Tbsp

10

Olive oil

1 Tbsp

8

Pistachios, dry roasted, salt added

1 oz (47 nuts)

3.7

Tea, brewed, prepared with tap water

6 fl oz

0.0

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.

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WebMD Medical Reference from Healthwise

Last Updated: April 10, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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