What is the recommended dose of vitamin K1 (phylloquinone) for a 6-year-old child?

Vitamin K Dose for a 6-Year-Old Child

For a 6-year-old child requiring vitamin K supplementation, the recommended dose is 1-10 mg/day of vitamin K1 (phylloquinone), with the specific dose within this range determined by the underlying indication and risk factors. 1

Dosing Framework by Clinical Context

For Routine Supplementation in At-Risk Conditions

• Standard dose: 1-5 mg/day for children with conditions predisposing to vitamin K deficiency (such as cystic fibrosis, fat malabsorption, or chronic antibiotic use) 1
• The ESPEN-ESPGHAN-ECFS guidelines specifically recommend 1-10 mg/day for "older children" (defined as beyond infancy), with dosing adjusted based on age and risk level 1

For Higher-Risk Scenarios

• Consider 5-10 mg/day for children with:
  • Documented low vitamin K levels 1
  • Liver disease 1
  • Severe malabsorption 1
  • Long-term broad-spectrum antibiotic therapy 1
• A well-performed study demonstrated that 5 mg daily effectively increased serum vitamin K1 levels in children with cystic fibrosis 1

Form and Administration

• Vitamin K1 (phylloquinone) is the preferred and safest form for supplementation, superior to menadione salts 1
• Daily administration is strongly preferred over weekly or intermittent dosing due to vitamin K's low storage capacity in the body 1
• Vitamin K1 has no known toxicity or adverse effects, making higher doses safe when clinically indicated 1

Monitoring Considerations

When to Measure Status

• Routine monitoring is not necessary for most children on prophylactic supplementation 1
• Measure vitamin K status when there is clinical suspicion of deficiency in conditions like cystic fibrosis, cholestasis, or unexplained bleeding 1

Preferred Biomarkers

• PIVKA-II (protein induced by vitamin K absence) is the most sensitive marker for subclinical deficiency and should be used when available 1, 2, 3
• Prothrombin time (PT) is insensitive and only becomes elevated in severe deficiency, making it inadequate for early detection 1
• Serum vitamin K concentrations, undercarboxylated osteocalcin, and matrix Gla protein are alternative markers but not routinely used due to cost 1

Critical Clinical Pitfalls

Common Dosing Errors to Avoid

• Do not use newborn/infant dosing (0.3-1 mg/day) for school-age children – this is insufficient for older children 1, 3
• Do not assume dietary intake is adequate in children with fat malabsorption, even if they consume green leafy vegetables, as absorption is impaired 1
• Do not use intermittent (weekly) dosing – the low storage capacity of vitamin K necessitates daily administration for consistent effect 1

High-Risk Populations Requiring Attention

• Children on anticoagulant therapy require careful monitoring if vitamin K is administered, as it can interfere with anticoagulant response 1, 4
• Exclusively breastfed infants transitioning to solid foods may still have suboptimal stores and warrant continued supplementation if risk factors persist 1, 2

Evidence Quality and Guideline Strength

The dosing recommendations come from ESPEN-ESPGHAN-ECFS guidelines published in Clinical Nutrition (2016), which acknowledge low-grade evidence for optimal vitamin K1 dosing in children 1. The broad range (1-10 mg/day) reflects this uncertainty, but the guidelines are clear that:

• The dose should be age-appropriate (higher for older children than infants) 1
• The dose should be risk-stratified (higher for those with documented deficiency or high-risk conditions) 1
• Safety is not a concern at any dose within this range, allowing clinicians to err on the side of adequacy 1

For a typical 6-year-old without severe malabsorption or liver disease, starting with 2-5 mg/day is reasonable, with upward titration to 5-10 mg/day if risk factors are present or if biochemical monitoring suggests inadequate response 1.