Supplement Forms/Alternate Names

  • Vitamin K1 (phylloquinone), vitamin K2 (menaquinone), vitamin K3 (menadione)

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

What Research Shows

Unlikely to Be Effective

Not Enough Data to Assess

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

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

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.

References

REFA Blood Clots

REFA1 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.

REFA2 Mahtani KR, Heneghan CJ, et al. Vitamin K for improved anticoagulation in patients receiving warfarin. Cochrane Database Syst Rev. 2014;(5):CD009917.

REFB Bone Strength

REFB1 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.

REFB2 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.

REFB3 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.

REFB4 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.

REFC Cardiometabolic Risk Factors

REFC1 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.

REFD Cardiovascular Disease

REFD1 Hartley L, Clar C, et al. Vitamin K for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2015;(9):CD011148.

REFE Cystic Fibrosis

REFE1 Jagannath VA, Fedorowicz Z, et al. Vitamin K supplementation for cystic fibrosis. Cochrane Database Syst Rev. 2011;(1):CD008482.

REFE2 Jagannath VA, Thaker V, et al. Vitamin K supplementation for cystic fibrosis. Cochrane Database Syst Rev. 2017 Aug 22;8:CD008482.

REFF Osteoporosis

REFF1 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.

REFF2 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.

Revision Information

  • Reviewer: EBSCO NAT Review Board Eric Hurwitz, DC
  • Review Date: 07/2019
  • Update Date: 03/27/2020