MedlinePlus Medical Encyclopedia: Vitamin K

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Vitamin K

Contents of this page:
Illustrations Alternative names Definition Function	Food Sources Side Effects Recommendations

Illustrations

Vitamin K benefit

Vitamin K source

Alternative names Return to top

Vitamin K deficiency; Deficiency - vitamin K

Definition Return to top

Vitamin K is a fat-soluble vitamin that plays an important role in blood clotting.

Function Return to top

Vitamin K is known as the clotting vitamin, because without it blood would not clot. Some studies indicate that it helps in maintaining strong bones in the elderly.

Food Sources Return to top

Vitamin K is found in cabbage, cauliflower, spinach and other green leafy vegetables, cereals, soybeans, and other vegetables. Vitamin K is also made by the bacteria that line the gastrointestinal tract.

Side Effects Return to top

Vitamin K deficiency is very rare and occurs when there is an inability to absorb the vitamin from the intestinal tract. Vitamin K deficiency can also occur after prolonged treatment with oral antibiotics.

Individuals with vitamin K deficiency usually have an increased propensity to bruising and bleeding.

Recommendations Return to top

Recommended dietary allowances (RDAs) are defined as the levels of intake of essential nutrients that the Food and Nutrition Board judges to be adequate to meet the known nutrient needs of almost all healthy persons.

Specific recommendations for each vitamin depend on age, gender, and other factors (such as pregnancy). The U.S. Department of Agriculture offers a PDF file that lists these recommendations.

The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods from the food guide pyramid.

It is important for people taking warfarin (a blood thinner) to know that vitamin K or foods containing vitamin K may reduce the effectiveness of this medication. Ask your health care provider before increasing intake or for advice on maintaining proper levels of vitamin K if you are taking warfarin.

Update Date: 1/19/2003

Updated by: Steven Angelo, M.D., Assistant Professor of Medicine, Yale School of Medicine, New Haven, CT. Review provided by VeriMed Healthcare Network.

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