In healthy subjects, there is no known safety risk associated with high doses of vitamin K1 (phylloquinone) or vitamin K2 (menaquinone) forms of vitamin K (27).

Tolerable upper intake levelsy

No tolerable upper level (UL) of intake has been established for vitamin K (27, 39).

Nutrient interactions

Large doses of vitamin A and vitamin E have been found to counteract vitamin K (5). Excess vitamin A appears to interfere with vitamin K uptake, whereas a form of vitamin E (tocopherol quinone) may inhibit vitamin K-dependent enzymes (40).

Drug interactions

Please note:

Because of the potential for interactions, dietary supplements should not be taken with medication (e.g., oral anticoagulants) without first talking to a knowledgeable healthcare provider.