Vitamin K

Other Name(s):

4-Amino-2-Methyl-1-Naphthol, Fat-Soluble Vitamin, Menadiol Acetate, Menadiol Sodium Phosphate, Menadione, Ménadione, Menadione Sodium Bisulfite, Menaquinone, Ménaquinone, Menatetrenone, Menatétrenone, Phytonadione, Methylphytyl Naphthoquinone, Phylloquinone, Phytomenadione, Vitamina K, Vitamine K, Vitamine Liposoluble, Vitamine Soluble dans les Graisses.


Vitamin K is a vitamin found in leafy green vegetables, broccoli, and Brussels sprouts. The name vitamin K comes from the German word "Koagulationsvitamin."

Several forms of vitamin K are used around the world as medicine. Vitamin K1 (phytonadione) and vitamin K2 (menaquinone) are available in North America. Vitamin K1 is generally the preferred form of vitamin K because it is less toxic, works faster, is stronger, and works better for certain conditions.

Vitamin K is most commonly used for blood clotting problems. For example, vitamin K is used to reverse the effects of "blood thinning" medications when too much is given. It is also used to prevent clotting problems in newborns who don't have enough vitamin K. Vitamin K is also given to treat and prevent vitamin K deficiency, a condition in which the body doesn't have enough vitamin K.

An increased understanding of the role of vitamin K in the body beyond blood clotting led some researchers to suggest that the recommended amounts for dietary intake of vitamin K be increased. In 2001, the National Institute of Medicine Food and Nutrition Board increased their recommended amounts of vitamin K slightly, but refused to make larger increases. They explained there wasn't enough scientific evidence to make larger increases in the recommended amount of vitamin K.

How does it work?

Vitamin K is an essential vitamin that is needed by the body for blood clotting, bone building, and other important processes.

Uses & Effectiveness

Effective for...

  • Preventing bleeding problems in newborns with low levels of vitamin K (hemorrhagic disease). Giving vitamin K1 by mouth or as a shot into the muscle helps prevent bleeding problems in newborns. Shots seem to work the best.
  • Treating and preventing bleeding problems in people with low levels of the blood clotting protein prothrombin. Taking vitamin K1 by mouth or as an injection into the vein can prevent and treat bleeding problems in people with low levels of prothrombin due to using certain medications.
  • An inherited bleeding disorder called vitamin K-dependent clotting factors deficiency (VKCFD). Taking vitamin K by mouth or as an injection into the vein can help prevent bleeding in people with VKCFD.
  • Reversing the effects of too much warfarin used to prevent blood clotting. Taking vitamin K1 by mouth or as in injection into the vein can reverse too much blood clotting caused by warfarin. However, injecting vitamin K1 under the skin does not seem to work. Taking vitamin K along with warfarin also seems to help stabilize blood clotting time in people taking warfarin. It works best in people who have low vitamin K levels.

Possibly Effective for...

  • Weak bones (osteoporosis). Taking a specific form of vitamin K2 seems to improve bone strength and reduce the risk of fracture in most older women with weak bones. But it doesn't seem to benefit older women who still have strong bones. Taking vitamin K1 seems to increase bone strength and might prevent fractures in older women. But it might not work as well in older men. Vitamin K1 doesn't seem to improve bone strength in women who have not gone through menopause or in people with Crohn's disease.

Possibly Ineffective for...

  • Bleeding within the fluid-filled areas (ventricles) of the brain (intraventricular hemorrhage). Giving vitamin K to women at risk for very preterm births does not seem to prevent bleeding in the brain of preterm infants. It also doesn't seem to reduce the risk of nerve injury caused by these bleeds.

Insufficient Evidence to Rate Effectiveness for...

  • Blood disorder (beta-thalassemia). Early research shows that taking vitamin K2 by mouth along with calcium and vitamin D can improve bone mass in children with this blood disorder.
  • Breast cancer. Research suggests that higher dietary intake of vitamin K2 is linked with a lower risk of developing breast cancer.
  • Cancer. Some research has linked a higher food intake of vitamin K2, but not vitamin K1, with a reduced risk of death from cancer. But other research has linked a higher food intake of vitamin K1, but not vitamin K2, with a reduced risk of death from cancer.
  • Colorectal cancer. Early research suggests that a higher dietary intake of vitamin K is not linked with a reduced risk of cancer of the colon and rectum.
  • Heart disease. Higher dietary intake of vitamin K2 has been linked with a reduced risk of heart disease, risk factors for heart disease, and death due to heart disease in older men and women. But vitamin K2 intake from food does not seem to be linked with a reduced risk a heart disease in people at high risk for this condition. Dietary intake of vitamin K1 has not been linked with a reduced risk of heart disease. But increasing vitamin K1 intake from food has been linked with a reduced risk of death due to heart disease. Also, taking vitamin K1 as a supplement seems to prevent or reduce the advancement of coronary calcification. This is a risk factor for heart disease.
  • Cystic fibrosis. People with cystic fibrosis can have low levels of vitamin K due to problems digesting fat. Taking a combination of vitamins A, D, E, and K seems to improve vitamin K levels in people with cystic fibrosis who have trouble digesting fat. Also, early research shows that taking vitamin K by mouth for can enhance the production of osteocalcin. Osteocalcin plays a role in the body's bone-building and metabolic regulation. But there is no reliable evidence suggesting that vitamin K improves overall health in people with cystic fibrosis.
  • Diabetes. Early research shows that taking a multivitamin fortified with vitamin K1 does not lower the risk of developing diabetes compared to taking a regular multivitamin.
  • Skin rash associated with a type of cancer medicine. People who are given a certain type of anticancer medicine often develop skin rash. Early research shows that applying a cream containing vitamin K1 helps prevent skin rash in people being given this type of medicine.
  • High cholesterol. There is early evidence that vitamin K2 might lower cholesterol in people on dialysis with high cholesterol levels.
  • Liver cancer. Taking vitamin K2 does not seem to prevent liver cancer recurrence. But some early research shows that taking vitamin K2 reduces the risk of liver cancer in people with liver cirrhosis.
  • Lung cancer. Early research suggests that higher intake of vitamin K2 from food is linked with a reduced risk of lung cancer and lung cancer-related death. Dietary intake of vitamin K1 does not seem to be linked with a reduced risk of these events.
  • Multiple sclerosis (MS). Interferon is a medicine that helps people with MS. This medicine often causes a rash and burning of the skin. Early research shows that applying vitamin K cream modestly reduces rash and burning in people with treated with interferon.
  • Prostate cancer. Early research suggests that higher dietary intake of vitamin K2, but not vitamin K1, is linked with a reduced risk of prostate cancer.
  • Rheumatoid arthritis. Early research shows that taking vitamin K2 along with arthritis medicine reduces markers of joint swelling better than taking arthritis medicine alone.
  • Stroke. Population research suggests that dietary intake of vitamin K1 is not linked with a reduced risk of stroke.
  • Bruises.
  • Burns.
  • Scars.
  • Spider veins.
  • Stretch marks.
  • Swelling.
  • Other conditions.
More evidence is needed to rate vitamin K for these uses.

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).


Next to red peppers, you can get the most vitamin C from ________________. See Answer

Side Effects

The two forms of vitamin K (vitamin K1 and vitamin K2) are LIKELY SAFE for most people when taken by mouth or injected into the vein appropriately. Most people do not experience any side effects when taking vitamin K in the recommended amount each day. However, some people may have an upset stomach or diarrhea.

Vitamin K1 is POSSIBLY SAFE for most people when applied as a cream that contains 0.1% vitamin K1.

Special Precautions & Warnings

Pregnancy and breast-feeding: When taken in the recommended amount each day, vitamin K is considered safe for pregnant and breast-feeding women. Don't use higher amounts without the advice of your healthcare professional.

Children: The form of vitamin K known as vitamin K1 is LIKELY SAFE for children when taken by mouth or injected into the body appropriately.

Diabetes: The form of vitamin K known as vitamin K1 might lower blood sugar levels. If you have diabetes and take vitamin K1, monitor your blood sugar levels closely.

Kidney disease: Too much vitamin K can be harmful if you are receiving dialysis treatments due to kidney disease.

Liver disease: Vitamin K is not effective for treating clotting problems caused by severe liver disease. In fact, high doses of vitamin K can make clotting problems worse in these people.

Reduced bile secretion: People with decreased bile secretion who are taking vitamin K might need to take supplemental bile salts along with vitamin K to ensure vitamin K absorption.


Warfarin (Coumadin)Interaction Rating: Major Do not take this combination.

Vitamin K is used by the body to help blood clot. Warfarin (Coumadin) is used to slow blood clotting. By helping the blood clot, vitamin K might decrease the effectiveness of warfarin (Coumadin). Be sure to have your blood checked regularly. The dose of your warfarin (Coumadin) might need to be changed.

Medications for diabetes (Antidiabetes drugs)Interaction Rating: Moderate Be cautious with this combination.Talk with your health provider.

Vitamin K1 might decrease blood sugar. Diabetes medications are also used to lower blood sugar. Taking vitamin K1 along with diabetes medications might cause your blood sugar to go too low. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.

Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), and others.


The following doses have been studied in scientific research:



  • For osteoporosis: The MK-4 form of vitamin K2 has been taken in doses of 45 mg daily. Also, vitamin K1 has been taken in doses of 1-10 mg daily.
  • For an inherited bleeding disorder called vitamin K-dependent clotting factors deficiency: 10 mg of vitamin K has been taken 2-3 times weekly.
  • For reversing the effects of warfarin: A single dose of 1-5 mg is typically used to reverse the effects of taking too much warfarin; however, the exact dose needed is determined by a lab test called the INR. Daily doses of 100-200 micrograms have been used for people taking warfarin long-term who have unstable blood clotting.
  • For an inherited bleeding disorder called vitamin K-dependent clotting factors deficiency: 10 mg of vitamin K has been injected into the vein. How often these injections are given is determined by a lab test called the INR.
  • For reversing the effects of warfarin: A single dose of 0.5-3 mg is typically used; however, the exact dose needed is determined by a lab test called the INR.


  • For preventing bleeding problems in newborns with low levels of vitamin K (hemorrhagic disease): 1-2 mg of vitamin K1 has been given in three doses over 8 weeks. Also single doses containing 1 mg of vitamin K1, 5 mg of vitamin K2, or 1-2 mg of vitamin K3 have been used.
  • For preventing bleeding problems in newborns with low levels of vitamin K (hemorrhagic disease): 1 mg of vitamin K1 has been given as a shot into the muscle.
There isn't enough scientific information to determine recommended dietary allowances (RDAs) for vitamin K, so daily adequate intake (AI) recommendations have been formed instead: The AIs are: infants 0-6 months, 2 mcg; infants 6-12 months, 2.5 mcg; children 1-3 years, 30 mcg; children 4-8 years, 55 mcg; children 9-13 years, 60 mcg; adolescents 14-18 years (including those who are pregnant or breast-feeding), 75 mcg; men over 19 years, 120 mcg; women over 19 years (including those who are pregnant and breast-feeding), 90 mcg.


Ageno, W., Crowther, M., Steidl, L., Ultori, C., Mera, V., Dentali, F., Squizzato, A., Marchesi, C., and Venco, A. Low dose oral vitamin K to reverse acenocoumarol-induced coagulopathy: a randomized controlled trial. Thromb.Haemost. 2002;88(1):48-51. View abstract.

Ageno, W., Garcia, D., Silingardi, M., Galli, M., and Crowther, M. A randomized trial comparing 1 mg of oral vitamin K with no treatment in the management of warfarin-associated coagulopathy in patients with mechanical heart valves. J.Am.Coll.Cardiol. 8-16-2005;46(4):732-733. View abstract.

Andersen, P. and Godal, H. C. Predictable reduction in anticoagulant activity of warfarin by small amounts of vitamin K. Acta Med.Scand. 1975;198(4):269-270. View abstract.

Bakhshi, S., Deorari, A. K., Roy, S., Paul, V. K., and Singh, M. Prevention of subclinical vitamin K deficiency based on PIVKA-II levels: oral versus intramuscular route. Indian Pediatr. 1996;33(12):1040-1043. View abstract.

Beker, L. T., Ahrens, R. A., Fink, R. J., O'Brien, M. E., Davidson, K. W., Sokoll, L. J., and Sadowski, J. A. Effect of vitamin K1 supplementation on vitamin K status in cystic fibrosis patients. J.Pediatr.Gastroenterol.Nutr. 1997;24(5):512-517. View abstract.

Bolton-Smith, C., McMurdo, M. E., Paterson, C. R., Mole, P. A., Harvey, J. M., Fenton, S. T., Prynne, C. J., Mishra, G. D., and Shearer, M. J. Two-year randomized controlled trial of vitamin K1 (phylloquinone) and vitamin D3 plus calcium on the bone health of older women. J.Bone Miner.Res. 2007;22(4):509-519. View abstract.

Booth, S. L., Broe, K. E., Gagnon, D. R., Tucker, K. L., Hannan, M. T., McLean, R. R., Dawson-Hughes, B., Wilson, P. W., Cupples, L. A., and Kiel, D. P. Vitamin K intake and bone mineral density in women and men. Am.J.Clin.Nutr. 2003;77(2):512-516. View abstract.

Booth, S. L., O'Brien-Morse, M. E., Dallal, G. E., Davidson, K. W., and Gundberg, C. M. Response of vitamin K status to different intakes and sources of phylloquinone-rich foods: comparison of younger and older adults. Am.J.Clin.Nutr. 1999;70(3):368-377. View abstract.

Boulis, N. M., Bobek, M. P., Schmaier, A., and Hoff, J. T. Use of factor IX complex in warfarin-related intracranial hemorrhage. Neurosurgery 1999;45(5):1113-1118. View abstract.

Braam, L. A., Knapen, M. H., Geusens, P., Brouns, F., and Vermeer, C. Factors affecting bone loss in female endurance athletes: a two-year follow-up study. Am.J.Sports Med. 2003;31(6):889-895. View abstract.

Braam, L. A., Knapen, M. H., Geusens, P., Brouns, F., Hamulyak, K., Gerichhausen, M. J., and Vermeer, C. Vitamin K1 supplementation retards bone loss in postmenopausal women between 50 and 60 years of age. Calcif.Tissue Int. 2003;73(1):21-26. View abstract.

Braam, L., McKeown, N., Jacques, P., Lichtenstein, A., Vermeer, C., Wilson, P., and Booth, S. Dietary phylloquinone intake as a potential marker for a heart-healthy dietary pattern in the Framingham Offspring cohort. J.Am.Diet.Assoc. 2004;104(9):1410-1414. View abstract.

Brophy, M. T., Fiore, L. D., and Deykin, D. Low-Dose Vitamin K Therapy in Excessively Anticoagulated Patients: A Dose-Finding Study. J.Thromb.Thrombolysis. 1997;4(2):289-292. View abstract.

Brousson, M. A. and Klein, M. C. Controversies surrounding the administration of vitamin K to newborns: a review. CMAJ. 2-1-1996;154(3):307-315. View abstract.

Byrd, D. C., Stephens, M. A., Hamann, G. L., and Dorko, C. Subcutaneous phytonadione for reversal of warfarin-induced elevation of the International Normalized Ratio. Am.J.Health Syst.Pharm. 11-15-1999;56(22):2312-2315. View abstract.

Cartmill, M., Dolan, G., Byrne, J. L., and Byrne, P. O. Prothrombin complex concentrate for oral anticoagulant reversal in neurosurgical emergencies. Br.J.Neurosurg. 2000;14(5):458-461. View abstract.

Cheung, A. M., Tile, L., Lee, Y., Tomlinson, G., Hawker, G., Scher, J., Hu, H., Vieth, R., Thompson, L., Jamal, S., and Josse, R. Vitamin K supplementation in postmenopausal women with osteopenia (ECKO trial): a randomized controlled trial. PLoS.Med. 10-14-2008;5(10):e196. View abstract.

Chow, C. K. Dietary intake of menaquinones and risk of cancer incidence and mortality. Am.J.Clin.Nutr. 2010;92(6):1533-1534. View abstract.

Cornelissen, E. A., Kollee, L. A., De Abreu, R. A., Motohara, K., and Monnens, L. A. Prevention of vitamin K deficiency in infancy by weekly administration of vitamin K. Acta Paediatr. 1993;82(8):656-659. View abstract.

Cornelissen, E. A., Kollee, L. A., De Abreu, R. A., van Baal, J. M., Motohara, K., Verbruggen, B., and Monnens, L. A. Effects of oral and intramuscular vitamin K prophylaxis on vitamin K1, PIVKA-II, and clotting factors in breast fed infants. Arch.Dis.Child 1992;67(10):1250-1254. View abstract.

Cornelissen, E. A., Kollee, L. A., van Lith, T. G., Motohara, K., and Monnens, L. A. Evaluation of a daily dose of 25 micrograms vitamin K1 to prevent vitamin K deficiency in breast-fed infants. J.Pediatr.Gastroenterol.Nutr. 1993;16(3):301-305. View abstract.

Crosier, M. D., Peter, I., Booth, S. L., Bennett, G., Dawson-Hughes, B., and Ordovas, J. M. Association of sequence variations in vitamin K epoxide reductase and gamma-glutamyl carboxylase genes with biochemical measures of vitamin K status. J.Nutr.Sci.Vitaminol.(Tokyo) 2009;55(2):112-119. View abstract.

Crowther, C. A., Crosby, D. D., and Henderson-Smart, D. J. Vitamin K prior to preterm birth for preventing neonatal periventricular haemorrhage. Cochrane.Database.Syst.Rev. 2010;(1):CD000229. View abstract.

Crowther, M. A., Donovan, D., Harrison, L., McGinnis, J., and Ginsberg, J. Low-dose oral vitamin K reliably reverses over-anticoagulation due to warfarin. Thromb.Haemost. 1998;79(6):1116-1118. View abstract.

Crowther, M. A., Douketis, J. D., Schnurr, T., Steidl, L., Mera, V., Ultori, C., Venco, A., and Ageno, W. Oral vitamin K lowers the international normalized ratio more rapidly than subcutaneous vitamin K in the treatment of warfarin-associated coagulopathy. A randomized, controlled trial. Ann.Intern.Med. 8-20-2002;137(4):251-254. View abstract.

Crowther, M. A., Julian, J., McCarty, D., Douketis, J., Kovacs, M., Biagoni, L., Schnurr, T., McGinnis, J., Gent, M., Hirsh, J., and Ginsberg, J. Treatment of warfarin-associated coagulopathy with oral vitamin K: a randomised controlled trial. Lancet 11-4-2000;356(9241):1551-1553. View abstract.

Dennis VC, Ripley TL, Planas LG, and Beach P. Dietary vitamin K in oral anticoagulation patients: clinician practices and knowledge in outpatient settings. J Pharm Technol 2008;24(2):69-76.

Dentali, F. and Ageno, W. Management of coumarin-associated coagulopathy in the non-bleeding patient: a systematic review. Haematologica 2004;89(7):857-862. View abstract.

Dentali, F., Ageno, W., and Crowther, M. Treatment of coumarin-associated coagulopathy: a systematic review and proposed treatment algorithms. J.Thromb.Haemost. 2006;4(9):1853-1863. View abstract.

Deveras, R. A. and Kessler, C. M. Reversal of warfarin-induced excessive anticoagulation with recombinant human factor VIIa concentrate. Ann.Intern.Med. 12-3-2002;137(11):884-888. View abstract.

Dezee, K. J., Shimeall, W. T., Douglas, K. M., Shumway, N. M., and O'malley, P. G. Treatment of excessive anticoagulation with phytonadione (vitamin K): a meta-analysis. Arch.Intern.Med. 2-27-2006;166(4):391-397. View abstract.

Dickson, R. C., Stubbs, T. M., and Lazarchick, J. Antenatal vitamin K therapy of the low-birth-weight infant. Am.J.Obstet.Gynecol. 1994;170(1 Pt 1):85-89. View abstract.

Dougherty, K. A., Schall, J. I., and Stallings, V. A. Suboptimal vitamin K status despite supplementation in children and young adults with cystic fibrosis. Am.J.Clin.Nutr. 2010;92(3):660-667. View abstract.

Drury, D., Grey, V. L., Ferland, G., Gundberg, C., and Lands, L. C. Efficacy of high dose phylloquinone in correcting vitamin K deficiency in cystic fibrosis. J.Cyst.Fibros. 2008;7(5):457-459. View abstract.

Duong, T. M., Plowman, B. K., Morreale, A. P., and Janetzky, K. Retrospective and prospective analyses of the treatment of overanticoagulated patients. Pharmacotherapy 1998;18(6):1264-1270. View abstract.

Eisai Co.Ltd. Eisai announces the intermediate analysis of anti-osteoporosis treatment post-marketing research to investigate the benefits of menatetrenone as part of the Ministry of Health, Labour and Welfare's Pharmacoepidemiological Drug Review Program. 2005;

Evans, G., Luddington, R., and Baglin, T. Beriplex P/N reverses severe warfarin-induced overanticoagulation immediately and completely in patients presenting with major bleeding. Br.J.Haematol. 2001;115(4):998-1001. View abstract.

Fetrow, C. W., Overlock, T., and Leff, L. Antagonism of warfarin-induced hypoprothrombinemia with use of low-dose subcutaneous vitamin K1. J.Clin.Pharmacol. 1997;37(8):751-757. View abstract.

Fondevila, C. G., Grosso, S. H., Santarelli, M. T., and Pinto, M. D. Reversal of excessive oral anticoagulation with a low oral dose of vitamin K1 compared with acenocoumarine discontinuation. A prospective, randomized, open study. Blood Coagul.Fibrinolysis 2001;12(1):9-16. View abstract.

Gijsbers, B. L., Jie, K. S., and Vermeer, C. Effect of food composition on vitamin K absorption in human volunteers. Br.J.Nutr. 1996;76(2):223-229. View abstract.

Glover, J. J. and Morrill, G. B. Conservative treatment of overanticoagulated patients. Chest 1995;108(4):987-990. View abstract.

Goldstein, J. N., Thomas, S. H., Frontiero, V., Joseph, A., Engel, C., Snider, R., Smith, E. E., Greenberg, S. M., and Rosand, J. Timing of fresh frozen plasma administration and rapid correction of coagulopathy in warfarin-related intracerebral hemorrhage. Stroke 2006;37(1):151-155. View abstract.

Greer, F. R., Marshall, S. P., Severson, R. R., Smith, D. A., Shearer, M. J., Pace, D. G., and Joubert, P. H. A new mixed micellar preparation for oral vitamin K prophylaxis: randomised controlled comparison with an intramuscular formulation in breast fed infants. Arch.Dis.Child 1998;79(4):300-305. View abstract.

Habu, D., Shiomi, S., Tamori, A., Takeda, T., Tanaka, T., Kubo, S., and Nishiguchi, S. Role of vitamin K2 in the development of hepatocellular carcinoma in women with viral cirrhosis of the liver. JAMA 7-21-2004;292(3):358-361. View abstract.

Hathaway, W. E., Isarangkura, P. B., Mahasandana, C., Jacobson, L., Pintadit, P., Pung-Amritt, P., and Green, G. M. Comparison of oral and parenteral vitamin K prophylaxis for prevention of late hemorrhagic disease of the newborn. J.Pediatr. 1991;119(3):461-464. View abstract.

Hogenbirk, K., Peters, M., Bouman, P., Sturk, A., and Buller, H. A. The effect of formula versus breast feeding and exogenous vitamin K1 supplementation on circulating levels of vitamin K1 and vitamin K-dependent clotting factors in newborns. Eur.J.Pediatr. 1993;152(1):72-74. View abstract.

Hosoi, T. [Treatment of primary osteoporosis with vitamin K2]. Clin.Calcium 2007;17(11):1727-1730. View abstract.

Hotta, N., Ayada, M., Sato, K., Ishikawa, T., Okumura, A., Matsumoto, E., Ohashi, T., and Kakumu, S. Effect of vitamin K2 on the recurrence in patients with hepatocellular carcinoma. Hepatogastroenterology 2007;54(79):2073-2077. View abstract.

Hung, A., Singh, S., and Tait, R. C. A prospective randomized study to determine the optimal dose of intravenous vitamin K in reversal of over-warfarinization. Br.J.Haematol. 2000;109(3):537-539. View abstract.

Hylek, E. M., Chang, Y. C., Skates, S. J., Hughes, R. A., and Singer, D. E. Prospective study of the outcomes of ambulatory patients with excessive warfarin anticoagulation. Arch.Intern.Med. 6-12-2000;160(11):1612-1617. View abstract.

Inoue, T., Fujita, T., Kishimoto, H., Makino, T., Nakamura, T., Nakamura, T., Sato, T., and Yamazaki, K. Randomized controlled study on the prevention of osteoporotic fractures (OF study): a phase IV clinical study of 15-mg menatetrenone capsules. J.Bone Miner.Metab 2009;27(1):66-75. View abstract.

Ishida, Y. [Vitamin K2]. Clin.Calcium 2008;18(10):1476-1482. View abstract.

Ishida, Y. and Kawai, S. Comparative efficacy of hormone replacement therapy, etidronate, calcitonin, alfacalcidol, and vitamin K in postmenopausal women with osteoporosis: The Yamaguchi Osteoporosis Prevention Study. Am.J.Med. 10-15-2004;117(8):549-555. View abstract.

Iwamoto, J. [Anti-fracture efficacy of vitamin K]. Clin.Calcium 2009;19(12):1805-1814. View abstract.

Iwamoto, J., Matsumoto, H., and Takeda, T. Efficacy of menatetrenone (vitamin K2) against non-vertebral and hip fractures in patients with neurological diseases: meta-analysis of three randomized, controlled trials. Clin.Drug Investig. 2009;29(7):471-479. View abstract.

Iwamoto, J., Sato, Y., Takeda, T., and Matsumoto, H. High-dose vitamin K supplementation reduces fracture incidence in postmenopausal women: a review of the literature. Nutr.Res. 2009;29(4):221-228. View abstract.

Iwamoto, J., Takeda, T., and Ichimura, S. Effect of combined administration of vitamin D3 and vitamin K2 on bone mineral density of the lumbar spine in postmenopausal women with osteoporosis. J.Orthop.Sci. 2000;5(6):546-551. View abstract.

Iwamoto, J., Takeda, T., and Ichimura, S. Effect of menatetrenone on bone mineral density and incidence of vertebral fractures in postmenopausal women with osteoporosis: a comparison with the effect of etidronate. J.Orthop.Sci. 2001;6(6):487-492. View abstract.

Iwamoto, J., Takeda, T., and Sato, Y. Role of vitamin K2 in the treatment of postmenopausal osteoporosis. Curr.Drug Saf 2006;1(1):87-97. View abstract.

Jie, K. S., Bots, M. L., Vermeer, C., Witteman, J. C., and Grobbee, D. E. Vitamin K intake and osteocalcin levels in women with and without aortic atherosclerosis: a population-based study. Atherosclerosis 1995;116(1):117-123. View abstract.

Jones, K. S., Bluck, L. J., Wang, L. Y., and Coward, W. A. A stable isotope method for the simultaneous measurement of vitamin K1 (phylloquinone) kinetics and absorption. Eur.J.Clin.Nutr. 2008;62(11):1273-1281. View abstract.

Jorgensen, F. S., Felding, P., Vinther, S., and Andersen, G. E. Vitamin K to neonates. Peroral versus intramuscular administration. Acta Paediatr.Scand. 1991;80(3):304-307. View abstract.

Kalkwarf, H. J., Khoury, J. C., Bean, J., and Elliot, J. G. Vitamin K, bone turnover, and bone mass in girls. Am.J.Clin.Nutr. 2004;80(4):1075-1080. View abstract.

Kazzi, N. J., Ilagan, N. B., Liang, K. C., Kazzi, G. M., Poland, R. L., Grietsell, L. A., Fujii, Y., and Brans, Y. W. Maternal administration of vitamin K does not improve the coagulation profile of preterm infants. Pediatrics 1989;84(6):1045-1050. View abstract.

Kim, H. S., Park, J. W., Jang, J. S., Kim, H. J., Shin, W. G., Kim, K. H., Lee, J. H., Kim, H. Y., and Jang, M. K. Prognostic values of alpha-fetoprotein and protein induced by vitamin K absence or antagonist-II in hepatitis B virus-related hepatocellular carcinoma: a prospective study. J.Clin.Gastroenterol. 2009;43(5):482-488. View abstract.

Klebanoff, M. A., Read, J. S., Mills, J. L., and Shiono, P. H. The risk of childhood cancer after neonatal exposure to vitamin K. N.Engl.J.Med. 9-23-1993;329(13):905-908. View abstract.

Knapen, M. H., Schurgers, L. J., and Vermeer, C. Vitamin K2 supplementation improves hip bone geometry and bone strength indices in postmenopausal women. Osteoporos.Int. 2007;18(7):963-972. View abstract.

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Kumar, D., Greer, F. R., Super, D. M., Suttie, J. W., and Moore, J. J. Vitamin K status of premature infants: implications for current recommendations. Pediatrics 2001;108(5):1117-1122. View abstract.

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Macdonald, H. M., McGuigan, F. E., Lanham-New, S. A., Fraser, W. D., Ralston, S. H., and Reid, D. M. Vitamin K1 intake is associated with higher bone mineral density and reduced bone resorption in early postmenopausal Scottish women: no evidence of gene-nutrient interaction with apolipoprotein E polymorphisms. Am.J.Clin.Nutr. 2008;87(5):1513-1520. View abstract.

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