Indicator Explainer
Vitamin K
The term "vitamin K" refers to a group of chemically similar fat-soluble compounds called naphthoquinones: vitamin K1 (phytonadione) is found in plants and is the primary source of vitamin K for humans through dietary consumption, vitamin K2 compounds (menaquinones) are made by bacteria in the human gut, and vitamin K3 (menadione) is a water-soluble preparation available for adults only. Vitamin K is necessary for the liver to produce the coagulation factors II, VII, IX, and X, as well as the clotting factors protein C, protein S, and protein Z; vitamin K deficiency can result in deficiencies of these coagulation factors and excess bleeding. An injection of vitamin K is routinely given to newborn infants to prevent vitamin K deficiency bleeding, also known as hemorrhagic disease of the newborn. Vitamin K deficiency is rare in adults but may result from chronic malnutrition or an inability to absorb dietary vitamins.
This page explains what the indicator is and how results are interpreted in general terms. Reference ranges depend on the laboratory, the method, and your own situation — no single “normal value” applies to everyone. This page is health information, not a diagnosis. For symptoms, treatment, or urgent concerns, contact a healthcare professional.
When it is tested
Source: National Cancer Institute, NCI Thesaurus 26.09d, C943. NCI definition, reproduced without modification under CC BY 4.0. Source identity and definition checked automatically on 2026-10-20. No individual clinical interpretation or human reviewer is asserted.
Reading results
Reference intervals and interpretation depend on the laboratory, specimen, method and clinical context. This source definition is educational information; it does not establish a diagnosis, product approval or suitability for an individual.