| Herbs & Supplements:

Vitamin K

Supplement Forms/Alternate Names
  • Vitamin K1 (phylloquinone), vitamin K2 (menaquinone), vitamin K3 (menadione)

 

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Introduction

Vitamin K is found in leafy greens, whole wheat, and oats. The body needs it for blood clotting and blood flow. Vitamin K has been used to clot blood and improve bone strength.

It can be taken as a pill or powder. It can also be injected into the bloodstream or muscle by a healthcare provider.

Dosages

1 to 2 milligrams daily

 

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What Research Shows

Unlikely to Be Effective

• Blood clots^{A1, A2} 

Not Enough Data to Assess

• Bone strength ^B1-B4 
• Cardiometabolic risk factors ^C1 
• Heart disease risk^D1 
• Cystic fibrosis ^{E1, E2} 
• Osteoporosis^{F1, F2} 

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

 

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Safety Notes

It is likely safe to take vitamin K in small doses for a short time. Not enough studies have been done to say whether it is safe to use for a long period.

Interactions

Talk to your doctor about any supplements or therapy you would like to use. Some can interfere with treatment or make conditions worse, such as:

• People taking blood thinners should talk to their doctors before taking vitamin K. It may interfere with the medicine.

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References [ + ]

A. Blood Clots

A1. Lam J, Schulman S, et al. Anticoagulation control with daily low-dose vitamin k to reduce clinically adverse outcomes and international normalized ratio variability: a systematic review and meta-analysis. Pharmacotherapy. 2013 Nov;33(11):1184-1190.

A2. Mahtani KR, Heneghan CJ, et al. Vitamin K for improved anticoagulation in patients receiving warfarin. Cochrane Database Syst Rev. 2014;(5):CD009917.

B. Bone Strength

B1. Cockayne S, Adamson J, et al. Vitamin K and the prevention of fractures: systematic review and meta-analysis of randomized controlled trials. Arch Intern Med. 2006;166(12):1256-1261.

B2. Knapen MH, Schurgers LJ, et al. Vitamin K2 supplementation improves hip bone geometry and bone strength indices in postmenopausal women. Osteoporos Int. 2007;18(7):963-972.

B3. Iwamoto J, Sato Y, et al. High-dose vitamin K supplementation reduces fracture incidence in postmenopausal women: a review of the literature. Nutr Res. 2009 Apr;29(4):221-228.

B4. Stevenson M, Lloyd-Jones M, et al. Vitamin K to prevent fractures in older women: systematic review and economic evaluation. Health Technol Assess. 2009;13(45):iii-xi.

C. Cardiometabolic Risk Factors

C1. Verma H, Garg R. Effect of Vitamin K Supplementation on Cardiometabolic Risk Factors: A Systematic Review and Meta-Analysis. Endocr Metab Immune Disord Drug Targets. 2019;19(1):13-25.

D. Cardiovascular Disease

D1. Hartley L, Clar C, et al. Vitamin K for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2015;(9):CD011148.

E. Cystic Fibrosis

E1. Jagannath VA, Fedorowicz Z, et al. Vitamin K supplementation for cystic fibrosis. Cochrane Database Syst Rev. 2011;(1):CD008482.

E2. Jagannath VA, Thaker V, et al. Vitamin K supplementation for cystic fibrosis. Cochrane Database Syst Rev. 2017 Aug 22;8:CD008482.

F. Osteoporosis

F1. Fang Y, Hu C, et al. Effect of vitamin K on bone mineral density: a meta-analysis of randomized controlled trials. J Bone Miner Metab. 2012 Jan;30(1):60-68.

F2. Huang ZB, Wan SL, et al. Does vitamin K2 play a role in the prevention and treatment of osteoporosis for postmenopausal women: a meta-analysis of randomized controlled trials. Osteoporos Int. 2015;26(3):1175-1186.

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Last reviewed July 2019 by EBSCO NAT Review Board Eric Hurwitz, DC
Last Updated: 3/27/2020

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