Unit Converter
Vitamin K (Phylloquinone)
(Essential Fat-Soluble Vitamin - Required for Coagulation, Bone Health & Vascular Physiology)
Synonyms
- Phylloquinone
- Vitamin K1
- K vitamin
- Anti-hemorrhagic vitamin
- 2-methyl-3-phytyl-1,4-naphthoquinone
- Part of the Vitamin K family (K1, K2 forms)
Note: Vitamin K1 = phylloquinone; Vitamin K2 = menaquinones (MK-4, MK-7), not measured routinely.
Units of Measurement
- nmol/L
- µg/L
- µg/dL
- µg/100 mL
- µg%
- ng/mL
Unit Conversions
Molecular Weight of Phylloquinone = 450.7 g/mol
nmol/L ↔ µg/L
1 nmol/L=0.451 µg/L1\ \text{nmol/L} = 0.451\ \text{µg/L}1 nmol/L=0.451 µg/L 1 µg/L=2.21 nmol/L1\ \text{µg/L} = 2.21\ \text{nmol/L}1 µg/L=2.21 nmol/L
µg/dL → µg/L
1 µg/dL=10 µg/L1\ \text{µg/dL} = 10\ \text{µg/L}1 µg/dL=10 µg/L
ng/mL → µg/L
1 ng/mL=1 µg/L1\ \text{ng/mL} = 1\ \text{µg/L}1 ng/mL=1 µg/L
µg/100 mL = µg% = µg/dL
Descrip tion
Vitamin K is a fat-soluble vitamin required for activation of several proteins involved in:
Coagulation
Vitamin K is the cofactor for γ-glutamyl carboxylase, which activates:
- Factors II, VII, IX, X
- Protein C
- Protein S
- Protein Z
Bone & Vascular Health
Carboxylates:
- Osteocalcin (bone mineral binding)
- Matrix Gla-protein (MGP) (prevents vascular calcification)
Phylloquinone (Vitamin K1)
Primary dietary form from green leafy vegetables.
Absorbed with fat; requires bile & pancreatic enzymes.
Why Vitamin K is tested
Used to investigate:
- Coagulopathy
- Malabsorption
- Warfarin therapy effects (indirect)
- Newborn hemorrhagic disease
- Liver disease contexts
Physiological Role
1. Activation of Clotting Proteins
Carboxylation converts inactive precursors → active coagulation factors.
2. Bone Formation
Vitamin K–dependent osteocalcin ensures proper bone mineralization.
3. Prevention of Vascular Calcification
Matrix Gla-protein (MGP) requires vitamin K for activation.
4. Antioxidant & Cellular Functions
Vitamin K participates in sphingolipid metabolism and anti-inflammatory pathways.
Clinical Significance
LOW VITAMIN K
Most common and clinically important.
Causes
- Malabsorption (cholestasis, CF, IBD, celiac disease, biliary obstruction)
- Long-term antibiotics (destroys gut bacteria)
- Warfarin therapy (vitamin K antagonist)
- Liver disease (decreased clotting factor synthesis)
- Newborns (low stores + sterile gut → risk for VKDB)
- Poor diet
- Pancreatic insufficiency
Symptoms
- Easy bruising
- Mucosal bleeding
- GI bleeding
- Hematuria
- Intracranial hemorrhage (infants)
- Prolonged PT/INR
HIGH VITAMIN K
Rare and usually due to supplements.
High intake is not toxic, but:
- May antagonize warfarin effect
- Very high doses of synthetic vitamin K3 (menadione, not used clinically) are hepatotoxic
Reference Intervals
(Tietz 8E • ARUP • Mayo • NIH)
Serum Phylloquinone (Vitamin K1)
- 0.15 – 1.5 ng/mL
(= 0.15 – 1.5 µg/L)
(= 0.33 – 3.3 nmol/L)
Deficiency
- <0.15 ng/mL
or - Elevated PT/INR despite adequate liver function
Newborns
Levels are low at birth → routine vitamin K prophylaxis recommended globally.
Diagnostic Uses
1. Evaluation of Bleeding Disorders
Especially with:
- Prolonged PT
- Normal aPTT
- Normal fibrinogen
Suggests vitamin K deficiency or early warfarin effect.
2. Assessment of Fat-Malabsorption
Cholestasis, CF, biliary disease.
3. Monitoring in Warfarin Therapy
Not measured directly, but deficiency influences INR.
4. Newborn Screening / Hemorrhagic Disease of the Newborn (VKDB)
5. Liver Disease Workup
6. Bone Metabolism Research
(Vitamin K’s role in osteocalcin carboxylation)
Analytical Notes
- Fasting sample recommended (post meal ↑ levels).
- Protect from light (phylloquinone degrades).
- LC-MS/MS is gold standard.
- Serum levels fluctuate with diet and lipoproteins; interpret with lipid profile if needed.
- PT/INR often a more clinically relevant functional indicator.
Clinical Pearls
- Warfarin inhibits vitamin K epoxide reductase, preventing recycling of active vitamin K.
- In cholestasis, deficiency occurs even with dietary adequacy → consider parenteral vitamin K.
- Vitamin K deficiency → prolonged PT earlier than aPTT.
- Breast-fed infants must receive vitamin K prophylaxis to prevent VKDB.
- Vitamin K2 (menaquinone) has longer half-life and more potent effects on bone, but Vitamin K1 is standard test analyte.
Interesting Fact
Vitamin K’s name comes from the German “Koagulations-Vitamin”, discovered in 1935 for its essential role in preventing hemorrhage.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Fat-Soluble Vitamins
- NIH Office of Dietary Supplements - Vitamin K
- WHO - Vitamin K prophylaxis guidelines
- Mayo Clinic Laboratories - Phylloquinone
- ARUP Consult - Vitamin K Testing
- British Society for Haematology (BSH) - Coagulation Guidelines