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).
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).
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.
Authored by Dr Peter Engel in 2010, reviewed and updated by Dr Szabolcs Peter on 18.06.2017