Vitamin K


In 1935 a scientist in Copenhagen observed that newly hatched chickens receiving a diet containing all of the known essential nutrients were developing a bleeding disorder. He soon discovered that the chicks were deficient in a nutrient that is crucial for normal blood clotting. He called this nutrient vitamin K. Today, vitamin K deficiency is rare, except in infants, for whom such a deficiency can be fatal.

The best sources of vitamin K are liver, green leafy vegetables and members of the cabbage family. Since vitamin K is also produced by bacteria in the intestines, humans are not dependent upon diet for this nutrient.

Dosage Info

Dosage Range

The dosage range is very broad; 10mcg to more than 10mg daily for certain bleeding conditions associated with anticoagulant medications have been used.

Most Common Dosage

Not able to be determined due to the varied doses associated with multiple medical conditions. It is estimated that most adults acquire the necessary RDA from a healthy diet. (1)

Dosage Forms

Tablets, capsules, and injectable (Rx only).

Interactions and Depletions



Reported Uses

Vitamin K plays a role in the function of several proteins that regulate the blood's ability to clot. (2) When the clotting mechanism is disrupted by medications like antibiotics, salicylates (aspirin) or excessive doses of oral anticoagulants (warfarin), vitamin K can be given to help correct the situation. (3) ,

Studies have indicated that vitamin K may help prevent some of the damaging effects that can occur with osteoporosis. Individuals who were given vitamin K or consumed more vitamin K in their diets had beneficial effects on maintaining their bone mineral density. (4) , (5) Other studies have shown a decrease in bone fractures in people using vitamin K. (6) One study evaluated the diets of over 72,000 women ranging in age from 38 to 63 years. This research found that the women who consumed greater amounts of vitamin K in their diets had a lower risk of hip fracture than the women who consumed lower amounts of vitamin K in their diets. (7)

Evidence has been found linking vitamin K status to atherosclerosis. (8) , (9) Postmenopausal women with blood vessel calcifications in their aorta had lower amounts of vitamin K in their bodies. (10) Research continues to determine if vitamin K can help prevent atherosclerosis.

A recent hypothesis has been proposed that vitamin K supplementation may have a beneficial effect in preventing or treating Alzheimer's disease. (11) More research is necessary.

Toxicities & Precautions


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This dietary supplement is considered safe when used in accordance with proper dosing guidelines.

Health Conditions

If you have clotting disorders, talk to your doctor before taking this dietary supplement. (12) , (13)

Side Effects

If the injectable form of this dietary supplement is to be given, talk to your healthcare professional before using this medication. (14)

Pregnancy / Breast Feeding

This vitamin crosses the placenta and is excreted into breast milk. (15) To date, the medical literature has not reported any adverse effects related to fetal development during pregnancy or to infants who are breast-fed. Proper nutrition is essential during pregnancy for the healthy development of the fetus. Numerous vitamins and minerals are a vital part of proper nutrition. If you are pregnant, think you might be pregnant, trying to get pregnant, or breast-feeding an infant, talk to your healthcare professional about supplementing your diet with appropriate vitamins and minerals.

Age Limitations

Vitamin K should not be used in premature infants or newborns without first talking to your healthcare professional. (16) Otherwise, the medical literature has not reported any adverse effects specifically related to the use of this dietary supplement in toddlers and children. Vitamins and minerals are an essential part of proper growth and development. Talk to your healthcare professional about the appropriate use of vitamins and minerals in children. Do not use any vitamin or mineral in children under 2 years of age unless first discussed with your healthcare professional.


  1. Panel on Micronutrients, Subcommittees on Upper Reference Levels of Nutrients and of Interpretation and Use of Dietary Reference Intakes, and the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press; 2001:144.
  2. View Abstract: Igarashi O. Vitamin K. Nippon Rinsho. Apr1993;51(4):910-18.
  3. aquaMEPHYTON (Phytonadione), Product Prescribing Information. Merck & Co., Inc. Whitehouse Station, NJ. May2001.
  4. View Abstract: Weber P. Vitamin K and bone health. Nutrition. Oct2001;17(10):880-7.
  5. View Abstract: Shiraki M, Shiraki Y, Aoki C, Miura M. Vitamin K2 (menatetrenone) effectively prevents fractures and sustains lumbar bone mineral density in osteoporosis. J Bone Miner Res. Mar2000;15(3):515-21.
  6. View Abstract: Iwamoto I, Kosha S, Noguchi S, Murakami M, Fujino T, Douchi T, Nagata Y. A longitudinal study of the effect of vitamin K2 on bone mineral density in postmenopausal women a comparative study with vitamin D3 and estrogen-progestin therapy. Maturitas. Jan1999;31(2):161-4.
  7. View Abstract: Feskanich D, Weber P, Willett WC, Rockett H, Booth SL, Colditz GA. Vitamin K intake and hip fractures in women: a prospective study. Am J Clin Nutr. Jan1999;69(1):74-9.
  8. View Abstract: Burnier JP, Borowski M, Furie BC, Furie B. Gamma-carboxyglutamic acid. Mol Cell Biochem. Sep1981;39:191-207.
  9. View Abstract: Kawashima H, Nakajima Y, Matubara Y, Nakanowatari J, Fukuta T, Mizuno S, et al. Effects of vitamin K2 (menatetrenone) on atherosclerosis and blood coagulation in hypercholesterolemic rabbits. Jpn J Pharmacol. Oct1997;75(2):135-43.
  10. View Abstract: Jie KS, Bots ML, Vermeer C, Witteman JC, Grobbee DE. Vitamin K intake and osteocalcin levels in women with and without aortic atherosclerosis: a population-based study. Atherosclerosis. Jul1995;116(1):117-23.
  11. View Abstract: Allison AC. The possible role of vitamin K deficiency in the pathogenesis of Alzheimer's disease and in augmenting brain damage associated with cardiovascular disease. Med Hypotheses. Aug2001;57(2):151-5.
  12. View Abstract: Byrd DC, Stephens MA, Hamann GL, Dorko C. Subcutaneous phytonadione for reversal of warfarin-induced elevation of the International Normalized Ratio. Am J Health Syst Pharm. Nov1999;56(22):2312-5.
  13. View Abstract: Patel RJ, Witt DM, Saseen JJ, Tillman DJ, Wilkinson DS. Randomized, placebo-controlled trial of oral phytonadione for excessive anticoagulation. Pharmacotherapy. Oct2000;20(10):1159-66.
  14. aquaMEPHYTON (Phytonadione), Product Prescribing Information. Merck & Co., Inc. Whitehouse Station, NJ. May2001.
  15. aquaMEPHYTON (Phytonadione), Product Prescribing Information. Merck & Co., Inc. Whitehouse Station, NJ. May2001.
  16. aquaMEPHYTON (Phytonadione), Product Prescribing Information. Merck & Co., Inc. Whitehouse Station, NJ. May2001.