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.
Also Known As
References
- NCI Thesaurus 26.09d — Vitamin K (C943)
- Source: National Cancer Institute, NCI Thesaurus 26.09d, C943. NCI definition, reproduced without modification under CC BY 4.0.
- Heavy menstrual bleeding with direct oral anticoagulants and vitamin K antagonists: a systematic review and meta-analysis. — Blood Coagul Fibrinolysis, 2026-10-20 (PMID 42895317; literature)
- Effect of Prothrombin Complex Concentrate versus Frozen Plasma on Divalent Cations and Vitamin K Dependent Factor Function: An Ex Vivo Mechanistic Study. — J Thromb Haemost, 2026-10-19 (PMID 42896657; literature)
- Reinventing vitamin K antagonist therapy management: an implementation study of a home-based integrated monitoring model. — Monaldi Arch Chest Dis, 2026-10-16 (PMID 42886161; literature)
- VKORC1L1 contributes to glioblastoma progression and temozolomide resistance by sustaining vitamin K reduction and limiting ferroptosis-associated lipid peroxidation. — Tissue Cell, 2026-10-13 (PMID 42913186; literature)
- Thiopurines and vitamin K antagonist resistance: warfarin inhibits thiopurine S-methyltransferase. — J Thromb Thrombolysis, 2026-10-25 (PMID 42927566; literature)
- Interpreting 'similar outcomes' in a small real-world comparison of apixaban and vitamin K antagonists. — Br J Clin Pharmacol, 2026-10-13 (PMID 42865142; literature)