MK-7: The Other Vitamin K

Publication Date: 
Tue, 11/08/2011
By: Alere Staff

Not all vitamin K is created equally. Vitamin K, sometimes referred to as K1, is not required to appear on labeling of food and beverages by the U.S. Food and Drug Administration (FDA). Vitamin K performs several roles in the body including helping the body in normal clotting functions as well as playing an important role in healthy bone development and bone maintenance.

Vitamin K1 is commonly found in familiar foods such as broccoli, spinach, and even parsley. Vitamin K1 is also found in popular cooking oils including canola and olive oil as well as some mayonnaise brands. For a comprehensive list of vitamin K1 foods visit our Vitamin K Finder.

The absorption of vitamin K1, is primarily absorbed by the body's liver with a relatively short half life (the availability of the active form of the vitamin). This means dietary vitamin K1 is not around very long in the body and generally cleared quickly.1

A new form of vitamin K has become available that patients need to know about. A commercially available, more concentrated form of vitamin K is now available in stores as an over the counter product and widely available on the internet. MK-7 (Menaquinone-7) is a vitamin K manufactured from fermented soybeans. Sometimes referred to as K2, MK-7 has been shown to have 10 times the absorption of K1. Unlike dietary vitamin K, MK-7 is absorbed through extra-hepatic tissues such as the arterial wall, pancreas and testes in men.2

All MK-7 forms of vitamin K are dangerous for patients taking brand Coumadin or generic warfarin. Manufacturers of MK-7 advise consumers not to use their product if they are taking warfarin. MK-7 is in the category of dietary supplement, which is monitored by the FDA but the safety is left up to the manufacturer.

More frequent testing of your INR may be neccessary to determine if an interaction with warfarin occured. As always, discuss all diet and supplements with your doctor.


  1. National Institutes of Health.
  2. Schurgers L, Teunissen K, Hamulya K, Knapen M, Vik H, Vermeer C. Vitamin K–containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood April 15, 2007 vol. 109 no. 8 3279-3283.