Ask the RCW Dietitian: Vitamin K and Warfarin

I’m on warfarin and have been told by my doctor to limit my intake of vitamin K. Which foods should I look out for?

Warfarin, which you may know by the brand name Coumadin, is a blood thinner that’s commonly prescribed to prevent blood clots that could lead to a stroke or heart attack.

Vitamin K is an important nutrient to consider when taking this medication as it helps the blood in our body clot. Too much vitamin K can cancel out the effects of blood-thinning medication.

Although some vitamin K is naturally produced by the bacteria in our intestines, we obtain higher amounts from certain foods. Foods that are especially high in vitamin K include:

  • Spinach

  • Kale

  • Brussels sprouts

  • Parsley

  • Collard greens

  • Cilantro

  • Green leaf or romaine lettuce

  • Broccoli

As you might notice, most foods that are high in vitamin K are dark, leafy greens, herbs, or vegetables.

If you’re taking warfarin/Coumadin, you don’t need to totally avoid vitamin K; however, the key is to be consistent with the amount of vitamin K you consume. If you don’t normally eat much of the above foods, don’t suddenly eat a large portion of them. This may mean reducing the proportion of these foods in a recipe if it’s something you don’t normally eat.

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