Phylloquinone (Vitamin K)

Phylloquinone in Serum

Clinical Information

Vitamin K is another fat soluble vitamin. It occurs as phylloquinone (main dietary form) and menaquinones. The latter is mostly produced by bacteria in the gut. Absorption rate of phylloquinone in free form is faster than that found in food1. Storage for vitamin K in the body is limited2.

Vitamin K is needed for the synthesis of proteins involved in blood clotting and helps regulates bone mineralization1,3.

Signs and Symptoms of Deficiency or Toxicity

Vitamin K is normally caused by fat malabsorptive syndromes. It may also be due to prolonged use of antibiotics that destroy vitamin K producing bacteria in the gut1.

Symptoms of vitamin K deficiency that has been reported include easy bruising, excessive bleeding, reduced prothrombin time, and increased risk to osteoporosis and fractures1,2.

At present, there are no known toxicities associated with intake of high doses of dietary or supplemental vitamin K2.

Biomarker and Methods of Analysis


Vitamin K1 (phylloquinone) in fasting serum is a strong indicator of dietary intake and status. Phylloquinone is the active bound form of vitamin K and is the major form that circulates in the bloodstream. It has been utilized on most researches as a biomarker to measure individuals’ vitamin K status. As a cofactor, phylloquinone is involved in the gamma-carboxylation of glutamate residues of several proteins 5.

Supplementation Guide

No established guidelines for supplementation of the general adult public.

No upper limit for vitamin K has been established for Filipinos. However, the International Alliance of Dietary/Food Supplement Associations (IDSA) suggests an observed safe level of 10 mg for adults6.

Vitamin K can interfere with anticoagulants. Its absorption may be affected by bile acid sequestrants1. Absorption may be impaired with excessive vitamin A intakes2.

Food Sources

In general, rich sources of vitamin K are green leafy vegetables. Examples are kale, spinach, broccoli, and lettuce. Oils like soybean and canola oil; fortified foods are also good sources1.

(1) Office of Dietary Supplements- National Institutes of Health. (n.d.) Vitamin K. Fact Sheet for Health Professionals. Retrieved from
(2) Higdon J, Drake VJ, Delage B. (July 2014). Vitamin K. Retrieved from
(3) Booth SL et al. Effect of vitamin K supplementation on bone loss in elderly men and women. Journal of Clin Endocrinol Metab 2008; 93:1217-1223.
(4) Shea MK and Booth SL. Concepts and controversies in evaluating vitamin K status in population-based studies. Nutrients 2016; 8; doi:10.3390/nu8010008
(5) Bralley, J.A., Lord, R.S. (2012). Laboratory Evaluations for Integrative and Functional Medicine. 2nd ed. Duluth, Ga: Metametrix Institute.
(6) Hathcock , John H. Safety of Vitamin and Minral Supplements. Safe Levels Identified by Risk Assessment. April 2004.