Vitamin K

The A-B-C's of Vitamin Supplements

Peer Reviewed

Vitamin capsule K isolated on white backgroundVitamin K is necessary for blood clotting, specifically the production of prothrombin; a plasma protein. Additionally, it is needed for bone formation and building osteocalcin, an important protein in bone tissue. Vitamin K may help prevent osteoporosis by increasing bone mass (especially in postmenopausal women).

In some cases, Vitamin K is given to reduce the risk of bleeding during or after long-term use of antibiotics or aspirin. Antibiotics, especially cephalosporins, reduce the absorption of vitamin K in the body. Vitamin K's clotting qualities may benefit women under treatment for heavy menstrual bleeding.

Newborn babies in the United States are routinely given an injection of Vitamin K following birth. The vitamin K given at birth provides protection against bleeding that could occur because of low levels of this essential vitamin.   

Dosage Guidelines
To make sure an adequate amount of vitamin K is consumed each day, consider these guidelines.
Vitamin K Table

Sources of Vitamin K
Significant amounts of vitamin K are found in the following foods: broccoli, Brussels sprouts, cabbage, cauliflower, chicken, green tea, turnip greens, dark green leafy vegetables, egg yolks, and asparagus. Cooking foods does not destroy vitamin K; however, freezing does.

Many forms of vitamin K are available (synthetic and natural). It is found in multivitamin formulas and in 5-mg tablet form. Water-soluble chlorophyll is most common and available without a prescription. This form may be useful to reduce body odor.

If anticoagulant medications (blood thinners such as warfarin, heparin or aspirin) are taken, consult a medical professional prior to taking vitamin K.

Vitamin E inhibits the body's ability to absorb vitamin K (aids in blood clotting), which may increase the risk of abnormal bleeding.

Pregnant women and nursing mothers should speak to a medical professional prior to taking vitamin K. Not only is the vitamin excreted in breast milk, but crosses the placenta. Do not take large doses of synthetic vitamin K during the last few weeks of pregnancy—it can result in a toxic reaction in the newborn.

The following increases the body's need for vitamin K: radiation therapy, long-term use of antibiotics and/or aspirin, phentoin, cholestryamine, and mineral oil laxatives.

Although vitamin K is generally nontoxic, if taking prescription medications, seek the advice of a medical professional first.


Disclaimer: Many people report feeling improvement in their condition and/or general well-being taking dietary, vitamin, mineral, and/or herbal supplements. The Editorial Board of, however, cannot endorse such products since most lack peer-reviewed scientific validation of their claims. In most cases an appropriate diet and a "multiple vitamin" will provide the necessary dietary supplements for most individuals. Prior to taking additional dietary, vitamin, mineral, and/or herbal supplements it is recommended that patients consult with their personal physician to discuss their specific supplement requirements.

Updated on: 03/10/16
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Thomas G. Lowe, MD
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