Vitamin K is found in green leafy vegetables, like spinach, kale, lettuce, watercress, parsley, broccoli and Swiss chard. It's also present in oils made from olives, soybeans, cottonseed and canola. Your body uses it for blood clotting, keeping bones healthy and cell growth. Although most forms of vitamin K are not toxic, one type used for vitamin K supplementation can be toxic.
Adequate Intake
The adequate intake levels set for vitamin K depend on your age and sex. The adequate intake for infants up to 6 months old is 2 mcg per day; for infants between 7 and 12 months old, 2.5 mcg per day; for children 1 to 3 years old, 30 mcg per day; for children 4 to 8, 55 mcg per day; for children 9 to 13, 60 mcg per day and for children 14 to 18, 75 mcg per day. For adults, men need 120 mcg per day and women need 90 mcg per day.
Toxicity Risk
There is no toxicity risk from consuming vitamin K-rich foods. Likewise, vitamin supplements containing vitamin K1 and vitamin K2 are safe even in high amounts when taken orally. However, vitamin K3, also known as menadione, can be toxic. It causes cell damage that can lead to liver toxicity, hemolytic anemia and jaundice, according to the Linus Pauling Institute.
Interactions and Warnings
Vitamin K interacts with warfarin. If you are taking this medication, keep your vitamin K intake consistent. CoQ10 also increases blood clotting, so be careful if you take these two supplements together, and avoid this combination if you take warfarin. High intake of vitamin K can also cause health problems if you have liver or kidney disease, according to MedlinePlus.
Considerations
Adults rarely become deficient in vitamin K unless they have some other health condition that causes this deficiency, according to the Food and Agriculture Organization of the United Nations. Most adults have an adequate intake from foods and don't need additional supplements. However, infants who don't receive a vitamin K shot shortly after birth are at risk for a deficiency that causes bleeding in the brain.
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