Managing My Vitamin K Consumption and My INR Values

Marshall Lev Dermer

Because I have atrial fibrillation, I take Warfarin so my blood coagulation time is between 2.0 (slower) and 3.0 (faster) on the INR scale. To remain in range, I daily balance my doctor-prescribed dose of Warfarin with my Vitamin K consumption. Vitamin K control is critical because Vitamin K reduces the effectiveness of Warfarin.

When I first began using Warfarin, my doctor advised me to select the kinds of foods I would eat daily. He did not ask me to reduce eating foods rich in Vitamin-K. Indeed, the recommended daily intake for Vitamin K is 90 and 120 mcg, for healthy women and men, respectively.

You don’t want to go below the recommended levels and you can, of course, consume more Vitamin K daily. What is important is keeping your level of Vitamin K consumption about the same from day to day. When you do this, your doctor can adjust your daily dose of Warfarin to your diet and so keep your INR values in range.

I discovered that I daily consumed about 150 mcg of Vitamin K from salads, asparagus, avocados, prunes, kiwis, a multiple vitamin, etc. How do I know?

First, I read labels. In particular, my multivitamin includes about 25 mcg of Vitamin K. For other sources, I found an app that accesses the Food and Nutrient Database of the USDA. As I have an Android smartphone, I have been using “Nutrition Facts.” Otherwise, you can access the database here.

If I wonder about the values that I see for a particular food, I will compare the values for the raw and frozen food as apparently freezing does not much affect Vitamin K. Or I might find another source for the value on the WWW, but it is possible that the other value also came from the USDA database!

Besides food, it is the case that drugs and herbs affect INR values. So, I consult with my physician about these. When in doubt my physician asks me to consume the new addition for three days and then have my INR assessed. BTW, this is what occurred for hot brewed oolong tea, my favorite tea. The hot brewed tea did not affect my INR scores. Worth noting, the USDA database reports that hot brewed oolong and hot brewed black tea contain less than 1 mcg of Vitamin K. As for hot brewed green tea, I found this “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.”

Besides the biomedical aspects of managing Warfarin there are social medical aspects. Some time ago, my wonderful family physician left to practice medicine closer to home and I wanted to somewhat increase my consumption of lettuce. But, my new, highly recommended physician was uncomfortable prescribing Warfarin with variable dosing. Specifically, I wanted the dose to be 2 mg for Monday and Thursday and 1.5 mg for the other days of the week.

She insisted on prescribing a constant dose of 2 mg daily despite my showing her articles from refereed journals that included variable dosing. Bottom line, if I were to take 2 mg daily my consumption of Vitamin K would have to dramatically increase.

What did I do? I asked my physician if I could have a hematologist prescribe Warfarin and monitor my INR values. My physician agreed and I think the hematologist (also an oncologist) was happy to see me, as my problem, so far, is only atrial fibrillation!

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