Coumadin and Vitamin K: What the Hell Is Going On with My INR and Other Questions Along Similar Lines

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George Gallup is a name everybody should know. He started the Gallup Poll, initially named the American Institute of Public Opinion, in 1935. He was famous, a year later, for predicting that Franklin Roosevelt would defeat Alf Landon in the U.S. presidential election, a noted contradiction to the well-respected Literary Digest magazine who sent out two million questionnaires and predicted that Landon would be the next president. 

Along similar lines, much like the Gallup poll, a study published in the Annals of Internal Medicine in 2013 quizzed a random population and revealed that half of all Americans use some form of vitamin supplementation. Vitamin sales nearly totaled a whopping $12 billion annually, including as many as two-thirds of older Americans, 50 and above, and those with higher levels of education. A line of demarcation exists between the docs who say that the overwhelming majority of vitamins are worthless and the docs who say they’re valuable to increase functioning of body parts. I say, who knows. 

But one vitamin stands out above the rest for people taking Coumadin, the blood thinner: vitamin K. A little background first.

Overall, Warfarin (the generic Coumadin) is a pill that I take regularly for two possible reasons: to help prevent blood clots or to keep a clot from getting bigger. To validate that Warfarin is diligently  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 breaks in the skin don’t bleed as much. Warfarin works against vitamin K, making your blood clot more slowly. 

So Warfarin and vitamin K work against each other along the lines of a battle that no one should win. When you take Warfarin, as my PCP says, it’s important that you eat the same amount of vitamin K every day. 

“If spinach is on sale at the Giant Eagle, don’t eat more amounts than you’re used to,” says the PCP. (Spinach is high in vitamin K).

I was living in New Jersey for almost two decades with an ex-partner who was an opinionated eater, healthy but opinionated. I made every shopping list the same and soon I didn’t need a list. After my stroke, the role shifted and my ex continued to buy the same things, healthy choices but the same choices. So my diet was well-controlled both before and after my stroke.

When I moved, I was on my own and that’s when the troubles began. I soon realized, just like a diabetic has to count sugars and carbohydrates, I have to count my vitamin K input. I bought what I wanted and didn’t know that I have to count. Now I know the secret.

If you already eat a lot of leafy green vegetables, that’s all right. 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 start dieting to lose weight, always keep the doctor informed so that the Warfarin can be adjusted.
You’re allowed 90 mcg (micrograms) of vitamin K every day. Notice the portion size and adjust accordingly. Here is a partial list, brought to you by WedMD:

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

(For more information on other foods and the amount of vitamin K in them, go to

If I didn’t eat vitamin K at all for that day, I’d eat three kiwis equaling 90 mcg, which I always have on hand.

There are only three foods that I know of that I can’t consume at all while I’m on Warfarin (I suspect for the rest of my life): cranberries, grapefruit, the latter in any form, and alcohol. (Farewell, rum fruitcake, my favorite food of all).

Check with the doc before you take any supplements or herbal products which may contain vitamin K.

To assess how well Warfarin is working, a blood test is needed every week or two to measure how long it takes for your blood to clot, until your blood result is stable.
Your lab results are called Prothrombin Time (PT) and International Normalized Ratio (INR) values. 

Your INR needs to be in a safe range–not too high to cause bleeding and not too low to cause clotting. Vitamin K can change how Warfarin works, which changes your INR. For me, and most people, the safety range is between 2.0 and 3.0. 

To summarize:
  • Vitamin K lowers your INR values. The lower your INR, the less time it takes for your blood to clot. A low INR means that warfarin isn’t working well enough to prevent a dangerous blood clot.
  • Warfarin raises your INR values. The higher your INR, the more time it takes for your blood to clot. A high INR means that warfarin is working too well, so you bleed more quickly and easily which can be dangerous. 

And from INR Tracker ( You’ll learn interesting things like 1 cup of granola has a little bit more than 10% of your daily Vitamin K needs. Or that you would have to eat 34 eggs to get 100% of your daily Vitamin K needs.
I’m moving toward stability by counting and eating the same amount of vitamin K daily. But it’s like I always said: It’s tough being a person.

Joyce Hoffman

Joyce Hoffman

Joyce Hoffman is one of the world's top 10 stroke bloggers according to the Medical News Today. You can find the original post and other blogs Joyce wrote in Tales of a Stroke Survivor. (
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