Vitamin D Dosing for Children
All infants should receive 400 IU of vitamin D daily starting soon after birth, and children/adolescents should receive 400-600 IU daily for maintenance, with higher doses (2000-6000 IU daily) reserved for treating documented deficiency.
Maintenance Dosing by Age Group
The most recent and authoritative guidelines from ESPGHAN/ESPEN/ESPR/CSPEN (2018) provide clear age-stratified recommendations 1:
Preterm Infants
- 200-1000 IU/day (or 80-400 IU/kg/day) for those on parenteral nutrition
- Target serum 25(OH)D concentration >50 nmol/L (>20 ng/mL)
Term Infants (0-12 months)
- 400 IU/day (or 40-150 IU/kg/day)
- This applies to all infants, including exclusively breastfed babies 2
- Should begin soon after birth
Children and Adolescents (>1 year)
- 400-600 IU/day for routine supplementation
- The American Academy of Pediatrics and Institute of Medicine recommend 600 IU/day for this age group 1
Treatment of Vitamin D Deficiency
When treating documented deficiency (25(OH)D <50 nmol/L or <20 ng/mL), substantially higher doses are required 3, 4:
Treatment Regimens
Daily dosing (preferred for compliance):
- Infants <1 year: 2000 IU/day for 12 weeks
- Children 1-18 years: 3000-6000 IU/day for 12 weeks
- Monitor 25(OH)D levels 3-6 months after initiating treatment 1
Alternative intermittent dosing (if daily compliance cannot be ensured, for children >6 months):
- 60,000 IU weekly for 6 weeks 3
- This approach should only be used when daily dosing is not feasible
Monitoring During Treatment
- Check serum 25(OH)D concentration 3-6 months after dose changes 1
- Target sufficiency: >50 nmol/L (>20 ng/mL) 1
- After repletion, transition to maintenance dosing (400-600 IU/day)
Special Populations Requiring Higher Doses
Children with conditions causing malabsorption or increased vitamin D metabolism need higher supplementation 5, 6:
- Chronic kidney disease: Individualized based on stage and 25(OH)D levels
- Cystic fibrosis: 800-2000 IU/day (up to 4000 IU/day for older children) 5
- Inflammatory bowel disease: Higher doses needed due to malabsorption 7
- On anticonvulsants or glucocorticoids: Maintain 25(OH)D >20 ng/mL with adjusted dosing 4
Safety Considerations
Upper tolerable limits established by the Institute of Medicine 1:
- 0-6 months: 1000 IU/day
- 7-12 months: 1500 IU/day
- 1-3 years: 2500 IU/day
- 4-8 years: 3000 IU/day
- 9-18 years: 4000 IU/day
Toxicity is rare and typically requires doses >10,000 IU/day for prolonged periods. Serum concentrations >375 nmol/L (>150 ng/mL) are associated with hypercalcemia and hyperphosphatemia 1.
Common Pitfalls to Avoid
Don't assume formula-fed infants get adequate vitamin D - Only those consuming ≥1 liter of fortified formula daily meet requirements without supplementation 2
Don't rely on sunlight exposure alone - Cutaneous synthesis is unreliable and varies by latitude, season, skin pigmentation, and sunscreen use 1, 2
Don't use active vitamin D analogs (calcitriol, alfacalcidol) to treat nutritional deficiency - These should be reserved for specific conditions like chronic kidney disease 6
Don't forget to supplement during weaning from parenteral nutrition - Oral supplementation should be considered during this transition 1
Don't routinely measure vitamin D levels in healthy children - Supplementation should be universal for infants; testing is reserved for those with risk factors or on long-term parenteral nutrition 1
Practical Implementation
For routine practice:
- Start all newborns on 400 IU/day vitamin D within days of birth
- Continue through adolescence at 400-600 IU/day
- Reserve testing for children with malabsorption, chronic diseases, or clinical signs of deficiency
- When deficiency is documented, treat with 2000-6000 IU/day (age-dependent) for 12 weeks, then return to maintenance dosing
The evidence strongly supports universal supplementation in infancy given the high prevalence of deficiency and the critical role of vitamin D in bone health, with emerging data suggesting broader health benefits 2, 8.