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Quality control and references

Quality Control and laboratory accreditation

KEQAS: vitamin K External Quality Assurance Scheme

This scheme assures the quality of laboratory measurements of phylloquinone, Vitamin K1, with the intention of harmonisation of methods for vitamin K analysis and their application to nutritional and clinical studies.

Participating laboratories receive four batches of three samples annually and are required to analyse them during specific periods over the course of the year. When results are returned they are subjected to statistical analysis including an outliers test and a Z scoring system. Members then receive comprehensive reports detailing their performance.

KEQAS is a UK NEQAS affiliated EQA scheme. Viapath Analytics LLP, operating KEQAS, is a UKAS accredited proficiency testing provider (No. 7586).

Laboratories interested in participating in the KEQAS scheme should contact David Card (

For more details on other laboratory accreditation, validation or proficiency testing schemes, please see the OpeN-Global page on Laboratory accreditation.

Technical assistance

  • For technical assistance and questions on vitamin K assessment, please contact OpeN-Global,
  • write to KEQAS, who provide technical advice for users of the supported laboratory methods. Contact: - more info on their Website.
  • Join the KEQAS LinkedIn group

Useful links

European Food Safety Authority (EFSA) Dietary reference values for vitamin K

NIH Factsheet for Health Professionals: Vitamin K 

WHO recommendations on newborn health 

Further reading

Booth SL, Rajabi AA 2008 Determinants of Vitamin K Status in Humans Vitamin K. Vol., 1-22.

Card DJ, Gorska R, Cutler J, Harrington DJ 2014 Vitamin K metabolism: current knowledge and future research. Mol Nutr Food Res 58:1590-1600.

Santorino D, Siedner MJ, Mwanga-Amumpaire J, Shearer MJ, Harrington DJ, Wariyar U 2015 Prevalence and Predictors of Functional Vitamin K Insufficiency in Mothers and Newborns in Uganda. Nutrients 7:8545-8552.

Shearer MJ, Fu X, Booth SL 2012 Vitamin K nutrition, metabolism, and requirements: current concepts and future research. Adv Nutr 3:182-195.

Theuwissen E, Magdeleyns EJ, Braam LA, Teunissen KJ, Knapen MH, Binnekamp IA, van Summeren MJ, Vermeer C 2014 Vitamin K status in healthy volunteers. Food Funct 5:229-234.

Tie JK, Stafford DW 2016 Structural and functional insights into enzymes of the vitamin K cycle. J Thromb Haemost 14:236-247.

Tsugawa N 2015 Cardiovascular Diseases and Fat Soluble Vitamins: Vitamin D and Vitamin K. Journal of nutritional science and vitaminology 61 Suppl:S170-172.


1.              Institute of Medicine (US) Panel on Micronutrients 2001 Chapter 5, Vitamin K, Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc.,. Vol. National Academies Press (US). Copyright 2001 by the National Academy of Sciences. All rights reserved., Washington (DC).

2.              Suttie JW, Booth SL 2011 Vitamin K. Adv Nutr 2:440-441.

3.              EFSA Panel on Dietetic Products NA 2017 Dietary reference values for vitamin K. EFSA Journal 15:e04780.

4.              Beulens JW, Booth SL, van den Heuvel EG, Stoecklin E, Baka A, Vermeer C 2013 The role of menaquinones (vitamin K(2)) in human health. Br J Nutr 110:1357-1368.

5.              Fu X, Harshman SG, Shen X, Haytowitz DB, Karl JP, Wolfe BE, Booth SL 2017 Multiple Vitamin K Forms Exist in Dairy Foods. Current Developments in Nutrition 1:e000638-e000638.

6.              Vermeer C, Raes J, van ‘t Hoofd C, Knapen MHJ, Xanthoulea S 2018 Menaquinone Content of Cheese. Nutrients 10.

7.              Gijsbers BL, Jie KS, Vermeer C 1996 Effect of food composition on vitamin K absorption in human volunteers. Br J Nutr 76:223-229.

8.              Lippi G, Franchini M 2011 Vitamin K in neonates: facts and myths. Blood Transfus 9:4-9.

9.              Shea MK, Booth SL 2016 Concepts and Controversies in Evaluating Vitamin K Status in Population-Based Studies. Nutrients 8.

10.           Jones KS, Bluck LJ, Wang LY, Coward WA 2008 A stable isotope method for the simultaneous measurement of vitamin K1 (phylloquinone) kinetics and absorption. European journal of clinical nutrition 62:1273-1281.