Vitamin K is a fat-soluble vitamin. It can be dissolved in fat. Vitamin K is carried through the body by fat and is stored in fat tissue. There are three forms of Vitamin K:

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The Recommended Dietary Allowance, called RDA, for vitamin K for adult males, age 25 years and older, is 80 micrograms (mcg) per day. For women, age 25 years and older, it is 65 mcg per day. For pregnant and lactating women, the RDA is also 65 mcg.

Vitamin K deficiency is rare. It is often the result of impaired absorption rather than not getting enough in the diet. Newborns are at risk for vitamin K deficiency. This is because their digestive tracts contain no vitamin K-producing bacteria. For this reason, doctors often give injections of vitamin K to newborns. The main symptom of vitamin K deficiency is blood that's slow to clot. Prolonged use of antibiotics can also cause a low level of this vitamin because they destroy some of the bacteria in the gut that help to produce vitamin K.

No symptoms are known to result from consuming too much vitamin K. Moderation is always the best approach. The most toxic form is supplements. People taking blood thinning medicines, such as aspirin or warfarin, may need to limit their intake of vitamin K-rich foods. This is because the vitamin's pro-clotting actions can work against this type of medicine.