Large doses of vitamin A and vitamin E have been found to antagonize vitamin K
(6). Excess vitamin A appears to interfere with vitamin K absorption, whereas a form of vitamin E (tocopherol quinone) may inhibit vitamin K-dependent carboxylase enzymes. One study in adults with normal
coagulation status found that supplementation with 1,000 IU of vitamin E for 12 weeks decreased gamma-carboxylation of prothrombin, a vitamin K-dependent protein
(51). A vitamin E-vitamin K interaction has also been reported in patients taking anticoagulatory drugs like warfarin.
Hemorrhage (excessive bleeding) was reported in a man taking 5 mg of warfarin and 1,200 IU of vitamin E daily
(52).