What you need to know about Vitamin K

What you need to know about Vitamin K

  • 17 Dec 0


The foods that you eat can affect how warfarin works in your body.  An important dietary measure is to try to be regular and consistent with your intake of vitamin K.  Very high or low amounts of dietary vitamin K may increase or decrease warfarin’s effect as vitamin K is an important part of the blood clotting process

Vitamin K is a vitamin (just like vitamin A, B, C, etc) that is found in all foods and your body even makes some vitamin K on its own (it is not potassium—this is abbreviated K+). The highest amount of vitamin K is found in green leafy vegetables like broccoli, different kinds of lettuce, cabbage, and spinach. 

A list of some of the foods that have a higher content of Vitamin K:


  • Asparagus (M) • Scallion, raw (H)
  • Avocado (M) • Kale, raw leaf (H)
  • Broccoli (H) • Lettuce (H)
  • Brussels Sprouts (H) • Mustard greens, raw (H)
  • Cabbage (H) • Parsley (H)
  • Cabbage, Red (M) • Peas, green, cooked (M)
  • Collard Greens (H) • Spinach, raw leaf (H)
  • Endive, raw (H) • Turnip greens, raw (H)
  • Watercress, raw (H)

Fats and Dressings* Condiments

  • Margarine (M) • Pickle Dill (M)
  • Mayonnaise (H)
  • Canola Oil (H)
  • Olive Oil (M)
  • Salad Oil (H)
  •  Soybean Oil (H)

*Please note that it takes a large quantity of fats and oils to reach a high amount of vitamin K

 (M) = Medium;   (H) = High

It is absolutely OK to eat these foods, and if you do, you don’t have to eat the same foods every day.  What you want to avoid is over-doing it, then under-doing it.  Try to spread the high content vitamin K foods though your week.  The main thing to remember is to try to keep your diet relatively consistent.  If you normally eat a salad every night for dinner (or every other night, or even just once a week) you can continue to do so and your warfarin dose can be adjusted accordingly. 

 Other dietary notes:

  • Alcohol can affect your warfarin therapy, but you do not necessarily need to avoid it altogether unless your anticoagulation provider has advised you to.  In general, alcohol intake should be limited to 1 drink per day (4 oz wine, 1.5 oz hard liquor, 12 oz beer).  Serious problems may occur with alcohol and warfarin when you drink more than 2 drinks a day or when you change your usual drinking pattern (i.e. binge drinking).  Be cautious during special occasions or holidays–drink only what you usually do on any day of the week. 
  • Grapefruit juice has no significant influence on warfarin dose requirements.
  • In the past, cranberries have been reported to affect warfarin doses in patients.  However, this theory has been proven false and it is absolutely OK to eat cranberries and drink cranberry juice as part of your normal diet.
  • I have seen dozens of probable mango-warfarin interactions.  There are only a few case reports in the medical literature and you probably won’t find many other medical providers that have heard about this.  However, it is possible that mango products (fresh, frozen, dried, juice) will cause a significant elevation in the INR and they are probably best avoided.

Check back soon…  upcoming blog topics include:

  • What is the INR?
  • Possible side effects with warfarin
  • OTC medicine interactions with warfarin
  • Common prescription medication interactions with warfarin
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