Vitamin K

    Written by:
    Thomas Solomon

    Fact-checked

    by:

    Nick Milazzo
    Last Updated: August 8, 2024

    Vitamin K is a fat-soluble vitamin that plays a key role in blood coagulation, bone metabolism, and vascular health. Vitamin K1 is found in many leafy greens and soy, while vitamin K2 is found in meat and fermented foods and is synthesized by intestinal bacteria. Supplementation with vitamin K improves markers of bone health, and vitamin K is administered to newborns to prevent vitamin K deficiency bleeding.

    128 references on this page
    27,732 participants in 24 trials and 12 meta-analyses

    Overview

    Dosage information

    Formulations:

    • Phylloquinone (vitamin K1)
    • Menaquinone-4 and menaquinone-7 (vitamin K2)
    • Menadione (vitamin K3) is rarely used in supplements.

    Range of dosages studied:

    • Phylloquinone (vitamin K1): 0.1–10 mg per day (mg/day), equivalent to 100–10,000 micrograms (μg) per day.
    • Menaquinone-4 (vitamin K2): 1–90 mg/day (1,000–90,000 μg/day).
    • Menaquinone-7 (vitamin K2): 0.09–2 mg/day (90–2,000 μg/day).

    Safety information:

    Vitamin K interacts with several drugs, including blood-thinning (anticoagulant) drugs like warfarin and drugs that affect the intestinal absorption of dietary fat, such as colesevelam and orlistat. Vitamin K absorption and metabolism can be impaired in people with hepatobiliary dysfunction. A tolerable upper intake level (UL) for vitamin K has not been set, because there is insufficient data assessing the risk.[1][2] This does not mean that taking an amount higher than the recommended dose is safe, just that current data does not find adverse effects.

    Dosage recommendation:

    The dosages that have been found to improve markers of bone health are 0.1–5 mg/day (100–5000 μg/day) of phylloquinone (vitamin K1), 15–45 mg/day of menaquinone-4 (vitamin K2), or 100–375 μg/day of menaquinone-7 (vitamin K2).[3][4][5]

    The adequate intake (AI) — the daily intake that ensures nutritional adequacy in most people — in micrograms (µg) per day for vitamin K is shown below.[1][2] Note that the AI for vitamin K varies slightly between countries; the data below are for the US.

    AgeMaleFemalePregnancyLactation
    0–6 months2.0 µg/day2.0 µg/day----
    7–12 months2.5 µg/day2.5 µg/day----
    1–3 years30 µg/day30 µg/day----
    4–8 years55 µg/day55 µg/day----
    9–13 years60 µg/day60 µg/day----
    14–18 years75 µg/day75 µg/day75 µg/day75 µg/day
    Older than 18 years120 µg/day90 µg/day90 µg/day90 µg/day

    Vitamin K is found in several foods. High amounts per serving are found in spinach, broccoli, kale, Brussels sprouts, collards, soybeans, etc.[6][7][8][9] Consult the FoodData Central database to check the amounts of vitamin K in the foods you eat.

    Take with food: Yes. Intestinal absorption of vitamin K appears to be improved in the presence of dietary fat.[10]

    Examine Database: Vitamin K

    Frequently asked questions

    Update History

    Examine Database References

    1. Bone Mineral Density - Fang Y, Hu C, Tao X, Wan Y, Tao FEffect of vitamin K on bone mineral density: a meta-analysis of randomized controlled trialsJ Bone Miner Metab.(2012 Jan)
    2. Bone Mineral Density - Iwamoto I, Kosha S, Noguchi S, Murakami M, Fujino T, Douchi T, Nagata YA longitudinal study of the effect of vitamin K2 on bone mineral density in postmenopausal women a comparative study with vitamin D3 and estrogen-progestin therapyMaturitas.(1999 Jan 4)
    3. Bone Mineral Density - Braam LA, Knapen MH, Geusens P, Brouns F, Vermeer CFactors affecting bone loss in female endurance athletes: a two-year follow-up studyAm J Sports Med.(2003 Nov-Dec)
    4. Bone Mineral Density - Knapen MH, Schurgers LJ, Vermeer CVitamin K2 supplementation improves hip bone geometry and bone strength indices in postmenopausal womenOsteoporos Int.(2007 Jul)
    5. Bone Mineral Density - Koitaya N, Sekiguchi M, Tousen Y, Nishide Y, Morita A, Yamauchi J, Gando Y, Miyachi M, Aoki M, Komatsu M, Watanabe F, Morishita K, Ishimi YLow-dose vitamin K2 (MK-4) supplementation for 12 months improves bone metabolism and prevents forearm bone loss in postmenopausal Japanese womenJ Bone Miner Metab.(2013 May 24)
    6. Bone Mineral Density - Binkley N, Harke J, Krueger D, Engelke J, Vallarta-Ast N, Gemar D, Checovich M, Chappell R, Suttie JVitamin K treatment reduces undercarboxylated osteocalcin but does not alter bone turnover, density, or geometry in healthy postmenopausal North American womenJ Bone Miner Res.(2009 Jun)
    7. Bone Mineral Density - Booth SL, Dallal G, Shea MK, Gundberg C, Peterson JW, Dawson-Hughes BEffect of vitamin K supplementation on bone loss in elderly men and womenJ Clin Endocrinol Metab.(2008 Apr)
    8. Bone Mineral Density - Knapen MH, Drummen NE, Smit E, Vermeer C, Theuwissen EThree-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal womenOsteoporos Int.(2013 Sep)
    9. Bone Mineral Density - Shea MK, Dallal GE, Dawson-Hughes B, Ordovas JM, O'Donnell CJ, Gundberg CM, Peterson JW, Booth SLVitamin K, circulating cytokines, and bone mineral density in older men and womenAm J Clin Nutr.(2008 Aug)
    10. Bone Mineral Density - Ushiroyama T, Ikeda A, Ueki MEffect of continuous combined therapy with vitamin K(2) and vitamin D(3) on bone mineral density and coagulofibrinolysis function in postmenopausal womenMaturitas.(2002 Mar 25)
    11. Bone Mineral Density - Nishiguchi S, Shimoi S, Kurooka H, Tamori A, Habu D, Takeda T, Kubo SRandomized pilot trial of vitamin K2 for bone loss in patients with primary biliary cirrhosisJ Hepatol.(2001 Oct)
    12. Bone Mineral Density - Mott A, Bradley T, Wright K, Cockayne ES, Shearer MJ, Adamson J, Lanham-New SA, Torgerson DJEffect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials.Osteoporos Int.(2019-Aug)
    13. Bone Mineral Density - Salma, Ahmad SS, Karim S, Ibrahim IM, Alkreathy HM, Alsieni M, Khan MAEffect of Vitamin K on Bone Mineral Density and Fracture Risk in Adults: Systematic Review and Meta-Analysis.Biomedicines.(2022 May 1)
    14. Liver Cancer Risk - Dariimaa Ganbat, Bat-Erdene Jugder, Lkhamaa Ganbat, Miki Tomoeda, Erdenetsogt Dungubat, Yoshihisa Takahashi, Ichiro Mori, Takayuki Shiomi, Yasuhiko TomitaThe Efficacy of Vitamin K, A Member Of Naphthoquinones in the Treatment of Cancer: A Systematic Review and Meta-AnalysisCurr Cancer Drug Targets.(2021)
    15. Liver Cancer Risk - Ishizuka M, Kubota K, Shimoda M, Kita J, Kato M, Park KH, Shiraki TEffect of menatetrenone, a vitamin k2 analog, on recurrence of hepatocellular carcinoma after surgical resection: a prospective randomized controlled trialAnticancer Res.(2012 Dec)
    16. Liver Cancer Risk - Toshihiko Mizuta, Iwata Ozaki, Yuichiro Eguchi, Tsutomu Yasutake, Seiji Kawazoe, Kazuma Fujimoto, Kyosuke YamamotoThe effect of menatetrenone, a vitamin K2 analog, on disease recurrence and survival in patients with hepatocellular carcinoma after curative treatment: a pilot studyCancer.(2006 Feb 15)
    17. Fracture Risk - Shiraki M, Shiraki Y, Aoki C, Miura MVitamin K2 (menatetrenone) effectively prevents fractures and sustains lumbar bone mineral density in osteoporosisJ Bone Miner Res.(2000 Mar)
    18. Bone Mineral Density - Xie C, Gong J, Zheng C, Zhang J, Gao J, Tian C, Guo X, Dai S, Gao TEffects of vitamin K supplementation on bone mineral density at different sites and bone metabolism in the middle-aged and elderly population.Bone Joint Res.(2024 Dec 11)
    19. Bone Mineral Density - Forli L, Bollerslev J, Simonsen S, Isaksen GA, Kvamsdal KE, Godang K, Gadeholt G, Pripp AH, Bjortuft ODietary vitamin K2 supplement improves bone status after lung and heart transplantationTransplantation.(2010 Feb 27)
    20. Bone Mineral Density - Purwosunu Y, Muharram, Rachman IA, Reksoprodjo S, Sekizawa AVitamin K2 treatment for postmenopausal osteoporosis in IndonesiaJ Obstet Gynaecol Res.(2006 Apr)
    21. Bone Mineral Density - Sasaki N, Kusano E, Takahashi H, Ando Y, Yano K, Tsuda E, Asano YVitamin K2 inhibits glucocorticoid-induced bone loss partly by preventing the reduction of osteoprotegerin (OPG)J Bone Miner Metab.(2005)
    22. Bone Mineral Density - Braam LA, Knapen MH, Geusens P, Brouns F, Hamulyák K, Gerichhausen MJ, Vermeer CVitamin K1 supplementation retards bone loss in postmenopausal women between 50 and 60 years of ageCalcif Tissue Int.(2003 Jul)
    23. Estrogen - Ozuru R, Sugimoto T, Yamaguchi T, Chihara KTime-dependent effects of vitamin K2 (menatetrenone) on bone metabolism in postmenopausal womenEndocr J.(2002 Jun)
    24. Glycemic Control - Hyung Jin Choi, MD, Juyoun Yu, BS, Hosanna Choi, BS, Jee Hyun An, MD, Sang Wan Kim, MD, PHD, Kyong Soo Park, MD, PHD, Hak C. Jang, MD, PHD, Seong Yeon Kim, MD, PHD and Chan Soo Shin, MD, PHDVitamin K2 Supplementation Improves Insulin Sensitivity via Osteocalcin Metabolism: A Placebo-Controlled Trial2011.()
    25. Weight - Zhao QY, Li Q, Hasan Rashedi M, Sohouli M, Rohani P, Velu PThe effect of vitamin K supplementation on cardiovascular risk factors: a systematic review and meta-analysis.J Nutr Sci.(2024)
    26. Weight - Nikpayam O, Jafari A, Faghfouri A, Pasand M, Noura P, Najafi M, Sohrab GEffect of Menaquinone-7 (MK-7) Supplementation on Anthropometric Measurements, Glycemic Indices, and Lipid Profiles: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.Prostaglandins Other Lipid Mediat.(2025 Mar)
    27. Insulin - Sakamoto N, Nishiike T, Iguchi H, Sakamoto KPossible effects of one week vitamin K (menaquinone-4) tablets intake on glucose tolerance in healthy young male volunteers with different descarboxy prothrombin levelsClin Nutr.(2000 Aug)
    28. Erythema - W W Lou, A T Quintana, R G Geronemus, M C GrossmanEffects of topical vitamin K and retinol on laser-induced purpura on nonlesional skinDermatol Surg.(1999 Dec)
    29. Erythema - Cohen JL, Bhatia ACThe role of topical vitamin K oxide gel in the resolution of postprocedural purpuraJ Drugs Dermatol.(2009 Nov)
    30. Bruising - Shah NS, Lazarus MC, Bugdodel R, Hsia SL, He J, Duncan R, Baumann LThe effects of topical vitamin K on bruising after laser treatmentJ Am Acad Dermatol.(2002 Aug)
    31. Bruising - Kovács RK, Bodai L, Dobozy A, Kemény LLack of the effect of topical vitamin K on bruising after mechanical injuryJ Am Acad Dermatol.(2004 Jun)
    32. Blood Pressure - Hartley L, Clar C, Ghannam O, Flowers N, Stranges S, Rees KVitamin K for the primary prevention of cardiovascular diseaseCochrane Database Syst Rev.(2015 Sep 21)
    33. Blood glucose - Suksomboon N, Poolsup N, Darli Ko Ko HEffect of vitamin K supplementation on insulin sensitivity: a meta-analysis.Diabetes Metab Syndr Obes.(2017)
    34. Osteocalcin - Geng C, Huang L, Pu L, Feng YEffects of vitamin K supplementation on vascular calcification in chronic kidney disease: A systematic review and meta-analysis of randomized controlled trials.Front Nutr.(2022)
    35. Insulin Resistance - Shahdadian F, Mohammadi H, Rouhani MHEffect of Vitamin K Supplementation on Glycemic Control: A Systematic Review and Meta-Analysis of Clinical Trials.Horm Metab Res.(2018 Mar)
    36. Insulin Resistance - Qu B, Yan S, Ao Y, Chen X, Zheng X, Cui WThe relationship between vitamin K and T2DM: a systematic review and meta-analysis.Food Funct.(2023 Oct 2)