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Look Up > Supplements > Vitamin K
Vitamin K
Dietary Sources
Commercial Preparations
Therapeutic Uses
Dosage Ranges and Duration of Administration
Side Effects/Toxicology


Vitamin K is fat-soluble and has an important role in making prothrombin and other proteins that help with blood clotting. Injections of vitamin K may be given before or after surgery to prevent hemorrhaging. Patients at risk of excessive bleeding because of liver disease, jaundice, malabsorption, or prolonged use of aspirin or antibiotics may also receive injections. Vitamin K has been used to treat heavy menstrual bleeding. It has also been used with vitamin C to treat morning sickness.

This vitamin is not readily transferred from mother to child. Without the intestinal bacteria necessary to synthesize vitamin K, newborns are at increased risk for hemorrhage. In these cases, newborns are often given vitamin K injections. Additionally, premature babies are at high risk for brain hemorrhage. Vitamin K supplements are often given to women at high risk of delivering prematurely. Women taking anti-epileptic drugs during pregnancy are often given supplements of vitamin K as their babies are at particular risk for deficiency. In the early 1990s, researchers reported a possible increase in risk for childhood cancers in children who were given vitamin K injections at birth. Results of recent studies, however, have been inconclusive. Some research suggests that oral supplements in three doses of 1 to 2 mg may be an acceptable alternative to injections.

Vitamin K inhibits the formation of calcium oxalate stones by synthesizing urinary proteins essential to kidney function. Vegetarians, whose diets are often high in vitamin K, have a low incidence of kidney stones.

Vitamin K is necessary for the conversion of osteocalcin, a protein that regulates the function of calcium in bone turnover and mineralization, to its active form. Vitamin K supplements may improve bone mineralization in postmenopausal women by increasing blood levels of osteocalcin and also by lowering the amount calcium excreted in the urine. Research suggests that vitamin K intakes much higher than the current recommendations improve biochemical markers of bone formation as well as bone density. Large supplemental doses of vitamin K have been useful in the treatment of osteoporosis. Low levels of vitamin K have been found in those with osteoporosis. In a Japanese study published in 1997, researchers found that, in a group of postmenopausal and peri-menopausal women with menopausal symptoms receiving hormone replacement therapy, those with reduced bone mineral density had lower levels of vitamin K1 and K2 than those with normal bone mineral density. Low levels of vitamin K have also been found in men with osteoporosis. A 1998 study suggested that vitamin K supplementation improves bone health in female elite athletes with amenorrhea. A 1998 study from the University of Pittsburgh suggests a synthetic form of vitamin K may stop liver cancer cell growth.

Dietary Sources
  • Chlorophyll
  • Green tea
  • Turnip greens
  • Broccoli
  • Spinach
  • Cabbage
  • Asparagus
  • Dark green lettuce

Freezing foods may destroy vitamin K. However, heating does not affect it.


Vitamin K occurs in three forms. Vitamin K1 (phylloquinone) is made by plants and is considered the preferred form; vitamin K2 (menaquinone) is made by animals, birds, and by bacteria in the intestinal tract; and vitamin K3 (menaphthone or menadione) is synthetic.

Commercial Preparations
  • Supplemental vitamin K is available in both natural and synthetic forms.
  • Supplements of fat-soluble chlorophyll are an excellent source of K1.
  • The water-soluble chlorophyll form of vitamin K is commonly sold in stores. Because this form cannot be absorbed in the gastrointestinal tract, its use is limited to the treatment of skin wounds.
  • K1 and K3 are available in multivitamin complexes, and as 5-mg tablets.
  • K1 injections are found in 2 mg/ml in 0.5-ml amps, and in 10 mg/ml in 1-ml ampules, and 2.5-ml and 5-ml vials.

Therapeutic Uses
  • Helps prevent hemorrhage in surgical patients.
  • Reduces risk of excessive bleeding in those with liver disease, jaundice, malabsorption and kidney disease.
  • Reduces excessive bleeding in those on long-term aspirin or antibiotic therapy.
  • Treats heavy menstrual bleeding.
  • Used with vitamin C to treat morning sickness.
  • Is a preventive measure for hemorrhage in newborns.
  • May prevent calcium oxalate stones in the kidney.
  • Supplements may improve bone mineralization.
  • Large supplemental doses have been used to treat osteoporosis.
  • A vitamin K analog, K compound 5, may stop liver cancer growth.
  • Some forms (water-soluble chlorophyll) helps to control body, fecal, and urinary odor.
  • Water-soluble forms are used in the treatment of skin wounds.

Dosage Ranges and Duration of Administration

Recommended dietary allowances (RDAs) are as follows.

  • Neonates to 6 months: 5 mcg
  • Infants 6 to 12 months:10 mcg
  • Children 1 to 3 years: 15 mcg
  • Children 4 to 6 years: 20 mcg
  • Children 7 to 10 years: 30 mcg
  • Men: 80 mcg
  • Women: 65 mcg
  • Pregnancy: 65 mcg
  • Lactation: 65 mcg

Three doses are recommended to prevent neonatal hemorrhage: 1 to 2 mg, the first given at the first feeding, the second at two to four weeks, and the third at eight weeks.

Side Effects/Toxicology

Natural vitamin K is rarely toxic. However, large amounts of menadione, a synthetic form of vitamin K, may cause liver damage and hemolytic anemia. Intravenous injection of vitamin K can cause flushing, sweats, chest pain, and constricted breathing. Hemolysis, jaundice, and hyperbilirubinemia have been observed in newborns after the administration of vitamin K. Pain, swelling, and eczema may result from intramuscular injections.

  • Vitamin K can interfere with the action of anticoagulants such as warfarin or coumadin.
  • X rays and radiation can raise vitamin K requirements.
  • Vitamin K is excreted in breast milk, and crosses the placenta. Use with caution in women who are pregnant or breast-feeding in conditions where there is concern for excess vitamin K.


In a crossover design clinical study, 13 healthy volunteers were maintained on a vitamin K1-restricted diet for 35 days and were randomly assigned to take omeprazole (40 mg/day) either during the first period of study or starting on day 15 until the end of the study (Paiva et al. 1998). The bacterial overgrowth induced by omeprazole included vitamin K2 (menaquinone)-synthesizing bacteria that served as a source of vitamin K. However, these bacteria were unable to restore vitamin K status to normal.


Phenytoin interferes with vitamin K metabolism (Keith et al. 1983). Clotting defects may occur in neonates born to mothers receiving anticonvulsant drugs (Solomon et al. 1977). Some researchers recommend supplementing with vitamin K in pregnant women on epileptic therapy four weeks before the expected date of delivery (Nulman et al. 1999). Other researchers have not found justification for giving vitamin K to all pregnant women on anticonvulsant therapy throughout the last trimester of pregnancy (Hey 1999).


Vitamin K can decrease the anticoagulant effect of warfarin by interfering with the production of vitamin K-dependent clotting factors (Bell et al. 1972; Hines Burnham et al. 2000). Oral vitamin K1 (phytonadione) is used to correct excessive anticoagulation in patients on warfarin therapy who do not have serious bleeding (Weibert et al. 1997). A prospective open label clinical study with 62 warfarin-treated patients that had elevated INR values found that vitamin K1 (1 mg po) was a safe, reliable, and economical means of reducing the INR in these patients (Crowther et al. 1998). A consistent dietary intake of vitamin K is important to maintain vitamin K status and avoid a potential warfarin-vitamin K interaction (Booth et al. 1997; Booth and Centurelli 1999). Patients should avoid drastic changes in dietary habits while on warfarin therapy. Individuals taking warfarin may require more intensive monitoring of vitamin K status and INR values.


Bell RG, Sadowski JA, Matschiner JT. Mechanism of action of warfarin. Warfarin and metabolism of vitamin K1. Biochem. 1972;11:1959-1961.

Bendich A, Decklebaum R. Preventive Nutrition: The Comprehensive Guide for Health Professionals. Totowa, NJ: Humana Press; 1997.

Booth SL, Centurelli MA. Vitamin K: a practical guide to the dietary management of patients on warfarin. Nutr Rev. 1999;57(9 Pt 1):288-293.

Booth SL, Charnley JM, Sadowski JA, Saltzman E, Bovill EG, Cushman M. Dietary vitamin K1 and stability of oral anticoagulation: proposal of a diet with constant vitamin K1 content. Thromb Haemost. 1997;77(3):504-509.

Craciun AM, Wolf J, Knapen MH, Brouns F, Vermeer C. Improved bone metabolism in female elite athletes after vitamin K supplementation. Int J Sports Med. 1998;19:479-484.

Crowther MA, Donovan D, Harrison L, McGinnis J, Ginsberg J. Low-dose oral vitamin K reliably reverses over-anticoagulation due to warfarin. Thromb Haemost. 1998;79:1116-1118.

Drug Facts and Comparisons 1999. St. Louis, Mo: Facts and Comparisons; 1998: 270-272.

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. 1999;69:74-79.

Hey E. Effect of maternal anticonvulsant treatment on neonatal blood coagulation. Arch Dis Child Fetal Neonatal Ed. 1999;81(3):F208-210.

Hines Burnham, et al, eds. Drug Facts and Comparisons. St. Louis, MO:Facts and Comparisons; 2000:179.

Jatoi A, Lennon C, O'Brien M, Booth SL, Sadowski J, Mason JB. Protein-calorie malnutrition does not predict subtle vitamin K depletion in hospitalized patients. Euro J Clin Nutri. 1998;52:934-937.

Jie KG, Bots ML, Vermeer C, Witteman JC, Grobbee DE. Vitamin K status and bone mass in women with and without aortic atherosclerosis: a population-based study. Calcif Tissue Int. 1996;59:352-356.

Keith DA, Gundberg CM, Japour A, et al. Vitamin-K dependent proteins and anticonvulsant medication. Clin Pharmacol Ther. 1983;34(4):529-532.

Kohlmeier M, Saupe J, Shearer MJ, Schaefer K, Asmus G. Bone health of adult hemodialysis patients is related to vitamin K status. Kidney Int. 1997;51:1218-1221.

Krummel D, Kris-Etherton P. Nutrition in Women's Health. Gaithersburg, Md: Aspen Publishers; 1996:434-435.

Lubetsky A, Dekel-Stern E, Chetrit A, Lubin F, Halkin H. Vitamin K intake and sensitivity to warfarin in patients consuming regular diets. Thromb Haemost. 1999;8:396-399.

Murray M. Encyclopedia of Nutritional Supplements. Rocklin, Calif: Prima Publishing; 1996:54-58.

Novel form of vitamin K may stop liver cancer cell growth. Oncology. 1998;12:1541.

Nulman I, Laslo D, Koren G. Treatment of epilepsy in pregnancy. Drugs. 1999;57(4):535-544. Published erratum appears in Drugs. 1999;57(6):870.

Paiva SAR, Sepe TE, Booth SL, et al. Interaction between vitamin K nutriture and bacterial overgrowth in hypochlorhydria induced by omeprazole. Am J Clin Nutr. 1998;68:699-704.

Reavley N. Vitamins etc. Melbourne, Australia: Bookman Press; 1998.

Shils ME, Olson JA, Shike M, Ross CA, eds. Modern Nutrition in Health and Disease. 9th ed. New York, NY: Lippincott, Williams & Wilkins; 1998.

Solomon GE, Hilgartner MW, Kutt H. Antivonvulsant-induced depression of clotting factors in children. Neurol Neurocir Psiquiatr. 1977;18(2-3 Suppl):277-284.

Tamatani M, Morimoto S, Nakajima M, et al. Decreased circulating levels of vitamin K and 25-hydroxyvitamin D in osteopenic elderly men. Metabolism. 1998;47:195-199.

Weibert RT, Le DT, Kayser SR, et al. Correction of excessive anticoagulation with low-dose oral vitamin K1. Ann Intern Med. 1997;126(12):959-962.

Which vitamin K preparation for the newborn? Drug Ther Bull. March 1998;36:17-19.

Copyright © 2000 Integrative Medicine Communications

This publication contains information relating to general principles of medical care that should not in any event be construed as specific instructions for individual patients. The publisher does not accept any responsibility for the accuracy of the information or the consequences arising from the application, use, or misuse of any of the information contained herein, including any injury and/or damage to any person or property as a matter of product liability, negligence, or otherwise. No warranty, expressed or implied, is made in regard to the contents of this material. No claims or endorsements are made for any drugs or compounds currently marketed or in investigative use. The reader is advised to check product information (including package inserts) for changes and new information regarding dosage, precautions, warnings, interactions, and contraindications before administering any drug, herb, or supplement discussed herein.