Vitamin K Dosing Frequency
For treating vitamin K deficiency, administer 1-2 mg orally once daily, while for reversing warfarin anticoagulation, a single dose is typically sufficient with repeat dosing only if INR remains elevated after 24 hours. 1, 2
Vitamin K Deficiency Treatment
Daily oral dosing is the standard approach:
- Administer 1-2 mg oral vitamin K daily for documented deficiency 1
- Continue treatment for at least 3 months, then recheck levels 1
- For patients who fail to respond to oral supplementation, refer for specialist assessment and consideration of intramuscular injections 1
- In bariatric surgery patients or those with malabsorption, parenteral routes (subcutaneous or IV) may be necessary from the outset 3
Maintenance dosing for prevention:
- Enteral nutrition should provide at least 3.5-20 mcg/100 kcal to meet daily requirements 1
- Parenteral nutrition should provide 150 mcg phylloquinone daily in addition to that present in lipid emulsions 1, 4
- Weekly IV supply of 250-500 mcg phylloquinone from lipids is sufficient to restore and maintain normal plasma levels 1
Warfarin Reversal Dosing Frequency
Single-dose strategy is preferred, with repeat dosing only if needed:
INR 5.0-9.0 Without Bleeding
- Give oral vitamin K 1-2.5 mg as a single dose 1, 2
- Recheck INR at 24 hours 1
- Repeat vitamin K only if INR remains >5.0 after 24 hours 1
- 95% of patients show INR reduction within 24 hours, with 85% achieving INR <4.0 5
INR >10 Without Bleeding
- Give oral vitamin K 2-2.5 mg as a single dose 1, 2, 6
- Recheck INR within 24 hours 1, 2
- Additional 1-2 mg may be given if INR remains high after 24 hours 1
- This single-dose approach reduces risk of INR >5 by day 3 (11.1% vs 46.7% with warfarin withdrawal alone) 2, 6
Serious Bleeding or Major Overdose (INR ≥20)
- Give vitamin K 10 mg by slow IV infusion (over 30 minutes) as initial dose 1, 7
- Supplement with fresh frozen plasma or prothrombin complex concentrate 1, 7
- May repeat 10 mg IV every 12 hours as needed based on INR response 1, 7
- Monitor INR every 6-8 hours initially 1, 7
Critical Dosing Considerations
Avoid high-dose vitamin K to prevent warfarin resistance:
- Doses >5 mg can cause warfarin resistance lasting up to one week, regardless of route 5, 2, 3
- This makes re-anticoagulation extremely difficult and should be avoided unless life-threatening bleeding exists 1, 2
Route selection matters for frequency:
- Oral vitamin K produces gradual, sustained effect over 24-48 hours, making once-daily dosing appropriate 5
- IV vitamin K acts faster but carries anaphylactoid reaction risk; reserve for emergencies 1, 8
- Subcutaneous route is unreliable and associated with cutaneous reactions; avoid this route 8
Special populations requiring adjusted frequency:
- Patients with malabsorption should receive parenteral vitamin K with INR monitoring every 1-2 days initially 3
- Mechanical heart valve patients with INR >6.0 should never receive IV vitamin K due to valve thrombosis risk; allow gradual INR decline with warfarin cessation instead 2
- Newborns receive a single prophylactic dose of 0.5-1 mg IM within one hour of birth 7
Common pitfall to avoid:
The most frequent error is giving repeated daily doses of vitamin K for warfarin reversal when a single dose would suffice. 1, 6 This practice stems from confusion between treating deficiency (which requires daily dosing) versus reversing anticoagulation (which typically needs only one dose with reassessment). 2, 8 Always recheck INR at 24 hours before administering additional doses. 1, 2