What You Should Know About Vitamin K and Blood Thinners

When you're taking blood-thinning medication, it's important to keep your vitamin K intake consistent so that the dose is just right. Here's what you need to know about vitamin K and blood thinners. 

Monica Reinagel, MS, LD/N, CNS
2-minute read

Vitamin K and Blood Thinners

Q. My aunt recently had a stroke and has been told to keep her daily vitamin K intake consistent. How can we easily keep track of dietary vitamin K ? 

A. It sounds as if your aunt is taking Coumadin, a blood-thinning medication that is often prescribed to prevent future strokes. Although Coumadin is a highly effective therapy, it's important that the dose be just right.  If the dose is too low, she is at increased risk of developing another blood clot. If the dose is too high, she runs the risk of excessive bleeding.

People taking Coumadin usually need regular blood tests to check their coagulation times and adjust their medication dose, if necessary. The amount of vitamin K in your aunt's diet will affect how much Coumadin she needs to take--and that's why it's important to avoid big swings (in either direction).

Leafy green vegetables, such as kale, collards, and spinach, are very high in vitamin K.  People taking Coumadin should avoid consuming large quantities of these vegetables, especially if they are not a regular part of their diets.  But, as I discussed in this episode, it's not necessary (or even advisable) to avoid all vegetables containing vitamin K. 

Ask the DivaYou can look up the vitamin K content of foods on the USDA Nutrient Database. Or, bookmark this handy reference guide I put together: Nutrition Diva's Vitamin K Cheat Sheet

For those taking Coumadin, try to keep vitamin K intake between  100 and 800 mcg per day. When you hit your limit for the day, simply choose vegetables that are not on the list for the rest of the day.  Also be sure to check any supplements you may be taking to see how much vitamin K they supply. 

Here is more information on vitamin K and Coumadin from the National Institutes of Health.

Image courtesy of Shutterstock


About the Author

Monica Reinagel, MS, LD/N, CNS

Monica Reinagel is a board-certified licensed nutritionist, author, and the creator of one of iTunes' most highly ranked health and fitness podcasts. Her advice is regularly featured on the TODAY show, Dr. Oz, NPR, and in the nation's leading newspapers, magazines, and websites. Do you have a nutrition question? Call the Nutrition Diva listener line at 443-961-6206. Your question could be featured on the show.