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
- 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.
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.