How do you diagnose and treat a patient with suspected vitamin K (Vit K) deficiency?

Diagnosis and Treatment of Vitamin K Deficiency

Diagnosis

Vitamin K deficiency should be diagnosed by combining serum phylloquinone (vitamin K1) levels with functional biomarkers, specifically PIVKA-II (undercarboxylated prothrombin), as no single gold standard test exists. 1

Laboratory Testing Approach

• Measure serum phylloquinone (vitamin K1): Deficiency is defined as levels <0.15 µg/L, which reflects short-term dietary intake and vitamin abundance 1, 2

• Measure PIVKA-II (Protein Induced by Vitamin K Absence): This is the most sensitive biomarker for functional vitamin K deficiency, detecting undercarboxylated prothrombin with reference range 17.4-50.9 mAU/mL 1, 2

• Use both tests in tandem: Phylloquinone indicates vitamin K abundance while PIVKA-II reveals cellular utilization, providing comprehensive assessment 1, 2

Clinical Indicators

• Prolonged PT with normal fibrinogen and platelet count is highly suggestive of vitamin K deficiency, particularly in bleeding patients 3

• Prolonged PT and aPTT together indicate deficiency affecting factors II, VII, IX, and X (all vitamin K-dependent) 3

• Do NOT rely on PT/INR alone for diagnosis—these tests lack sensitivity for detecting subclinical deficiency and are erroneously used for this purpose 1

High-Risk Populations to Screen

• Patients with steatorrhea or fat malabsorption 1
• Prolonged broad-spectrum antibiotic use (especially cephalosporins) 1, 4
• Chronic kidney disease 1
• Malnutrition or restricted diet 1
• Chronic gastrointestinal disorders (Crohn's disease involving ileum, ulcerative colitis on sulfasalazine) 5
• Patients on warfarin therapy 1
• Neonates without vitamin K prophylaxis 3, 6

Confirmatory Testing

• Response to vitamin K administration: Correction of PT/aPTT within 2-4 hours after vitamin K administration confirms the diagnosis 3, 7, 4

• Mixing studies: Decrease in PT when patient plasma is mixed with normal plasma supports vitamin K deficiency over inhibitor-mediated coagulopathy 4

Treatment

For vitamin K deficiency, treat with 1-2 mg oral vitamin K daily (phytomenadione, menadiol sodium phosphate, or Ketovite tablets), and recheck levels after 3 months. 8

Adult Treatment Regimens

Mild to moderate deficiency:

• Oral vitamin K 1-2 mg daily for 3 months 8
• Recheck levels after 3 months 8

Severe deficiency or coagulopathy:

• Initial dose: 2.5-25 mg vitamin K (rarely up to 50 mg may be required) 7
• Route depends on severity: subcutaneous preferred, intravenous if unavoidable (not exceeding 1 mg per minute) 7
• Expect PT correction within 2-4 hours; if not improved in 6-8 hours, repeat the dose 7

Life-threatening bleeding:

• Administer vitamin K 1 mg subcutaneously or intramuscularly immediately 3, 7
• Give Fresh Frozen Plasma (FFP) 10-20 mL/kg for immediate factor replacement while awaiting vitamin K effect 3
• FFP provides temporary hemostasis but does not address underlying deficiency 3

Neonatal Treatment

Prophylaxis (Hemorrhagic Disease of the Newborn):

• Single intramuscular dose of 0.5-1 mg vitamin K within one hour of birth 7

Treatment of active bleeding in newborns:

• Vitamin K 1 mg subcutaneously or intramuscularly 7
• Higher doses may be necessary if mother received oral anticoagulants 7
• Expect PT shortening within 2-4 hours as diagnostic confirmation 7

Special Considerations

Patients on warfarin:

• Refer to specialist for assessment, as vitamin K dosing must be carefully balanced with anticoagulation needs 8

Non-responders to oral therapy:

• Refer to specialist for assessment and consideration of intramuscular injections 8

Patients with hepatic dysfunction:

• May require higher doses due to decreased synthesis of vitamin K-dependent factors 3

Important Caveats

• Large vitamin E doses can exacerbate vitamin K deficiency and affect coagulation, so assess vitamin K status when treating vitamin E deficiency 8

• Benzyl alcohol-containing diluents should not be used in newborns due to toxicity risk 7

• Vitamin K administration should be immediate in suspected deficiency with bleeding—do not delay for confirmatory testing 3, 7

• Older patients on prolonged antibiotics are at particularly high risk and require proactive monitoring and supplementation 4

• Clinically significant bleeding from vitamin K deficiency typically only occurs in newborns or with extreme malabsorption 1