What vitamin D supplementation dose should be given to a pediatric patient—from birth to 18 years—and how should the regimen be adjusted for documented deficiency or risk factors such as limited sun exposure, exclusive breastfeeding, darker skin, obesity, or chronic illness?

Vitamin D Supplementation Dosing for Pediatric Patients

Standard Maintenance Dosing by Age

All infants from birth to 12 months should receive 400 IU of vitamin D daily starting at hospital discharge, and all children and adolescents aged 1-18 years should receive 600 IU daily. 1, 2

Infants (0-12 months)

• 400 IU/day for all infants, regardless of feeding method 1, 2
• Breastfed infants: Begin 400 IU/day at hospital discharge and continue throughout breastfeeding 2
• Formula-fed infants: Continue 400 IU/day until consistently consuming ≥28 ounces (840 mL) of vitamin D-fortified formula daily 2
• Mixed-fed infants: Continue 400 IU/day until reliably consuming ≥28 ounces of formula daily 2

Children and Adolescents (1-18 years)

• 600 IU/day from all sources (diet plus supplements) 1

Preterm Infants

• 200-1,000 IU/day (or 80-400 IU/kg/day) for preterm infants, particularly those on parenteral nutrition 3, 1, 2
• Extremely preterm infants may require up to 800-1,000 IU/day 2

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Treatment of Documented Vitamin D Deficiency

For children with documented deficiency, use a loading dose regimen of 2,000 IU daily for 12 weeks (or 50,000 IU every other week for 12 weeks), followed by age-appropriate maintenance dosing. 4

Deficiency Classification and Treatment

• Severe deficiency (<5 ng/mL): 4,000 IU/day for 12 weeks OR 50,000 IU every other week for 12 weeks 4, 1
• Mild deficiency (5-15 ng/mL): 4,000 IU/day for 12 weeks OR 50,000 IU every other week for 12 weeks 4, 1
• Insufficiency (16-30 ng/mL): 2,000 IU/day for 12 weeks OR 50,000 IU every 4 weeks 4, 1

Post-Treatment Maintenance

• After completing the 12-week loading phase, transition to 600 IU/day for children 1-18 years 4, 1
• Recheck 25(OH)D levels after 12 weeks to confirm normalization (target >20 ng/mL or 50 nmol/L) 4, 1
• Monitor levels every 6-12 months, especially during winter months 4

Essential Co-Interventions

• Provide 250-500 mg/day of elemental calcium during vitamin D treatment to support bone mineralization and prevent hypocalcemia, particularly in children with low ionized calcium or elevated PTH 4
• Evaluate serum calcium, phosphorus, alkaline phosphatase, and PTH levels to assess for metabolic bone disease 4
• For children with clinical rickets, consider orthopedic consultation for severe bone deformities 4

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Adjustments for High-Risk Populations

Exclusive Breastfeeding

• Begin 400 IU/day at hospital discharge and continue throughout the breastfeeding period, as breast milk provides insufficient vitamin D (typically <25-78 IU/L) 2
• Alternative: Lactating mothers can take 6,400 IU/day, which provides adequate vitamin D to the infant through breast milk 2

Limited Sun Exposure

• Maintain standard 400-600 IU/day dosing based on age, as safe sun exposure is unreliable due to skin cancer prevention guidelines, seasonal variation, and geographic latitude 2
• Children with limited outdoor time require closer monitoring but not necessarily higher routine dosing 4

Darker Skin Pigmentation

• Standard dosing (400-600 IU/day) is appropriate, but these children require closer monitoring of vitamin D levels, particularly in northern latitudes 4
• Consider checking 25(OH)D levels if multiple risk factors are present 4

Obesity

• Obese children may require higher doses due to sequestration in adipose tissue, though specific pediatric dosing is not well-established 4
• Monitor 25(OH)D levels more frequently (every 6-12 months) in obese children on supplementation 4

Chronic Illness

• Malabsorption conditions (celiac disease, inflammatory bowel disease, cystic fibrosis, chronic diarrhea): Check 25(OH)D levels and consider higher supplementation doses 4
• Chronic kidney disease (CKD stages 3-5): May require higher or more frequent supplementation with close monitoring of calcium and phosphorus to avoid hypercalcemia 4, 1
• Nephrotic syndrome: Monitor ionized calcium, 25(OH)D, and PTH closely due to urinary losses of vitamin D-binding protein; supplement with cholecalciferol PLUS calcium (250-500 mg/day) when levels are low 4
• Long-term parenteral nutrition: Monitor 25(OH)D periodically and provide additional supplementation if levels fall below 50 nmol/L (20 ng/mL) 4, 1

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Formulation Selection

Cholecalciferol (vitamin D3) is strongly preferred over ergocalciferol (vitamin D2) due to higher bioefficacy and bioavailability. 4, 1, 2

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Safety Thresholds and Upper Tolerable Limits

The Institute of Medicine established age-specific upper limits to prevent toxicity 1:

• 0-6 months: 1,000 IU/day maximum 1, 2
• 7-12 months: 1,500 IU/day maximum 1, 2
• 1-3 years: 2,500 IU/day maximum 1
• 4-8 years: 3,000 IU/day maximum 1
• 9-18 years: 4,000 IU/day maximum 1

Prolonged daily intake up to 10,000 IU appears safe, but serum concentrations >375 nmol/L are associated with acute hypercalcemia and hyperphosphatemia. 4

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Target Serum Levels and Monitoring

Target Levels

• Goal: 25(OH)D >20 ng/mL (50 nmol/L) for bone health and sufficiency 4, 1, 2
• Optimal levels may be 30 ng/mL according to some guidelines, though this is debated 4

Monitoring Strategy

• Routine testing is NOT recommended for healthy infants and children receiving appropriate supplementation 2
• Targeted testing is indicated for:
  • Malabsorption conditions (celiac disease, IBD, cystic fibrosis, chronic diarrhea) 4
  • Chronic kidney disease (annual monitoring) 4
  • Long-term parenteral nutrition (periodic monitoring) 4, 1
  • Maternal deficiency, dark skin, or exclusive breastfeeding without supplementation 2
  • Children on treatment doses (recheck after 12 weeks) 4
• For children on supplementation at or above upper tolerable limits, monitor serum 25(OH)D every 3-6 months 4

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Common Pitfalls and How to Avoid Them

• Do not delay supplementation until the first outpatient visit—begin at hospital discharge 2
• Do not assume formula-fed infants receive adequate vitamin D until they consistently consume ≥28 ounces (840 mL) of fortified formula daily 2
• Ensure adherence to the supplementation regimen, as inconsistent supplementation is a common cause of treatment failure 4
• Do not use active vitamin D analogs (calcitriol) to treat nutritional vitamin D deficiency 4
• Do not compromise calcium intake during vitamin D treatment, especially in children with nephrotic syndrome or rickets 4
• Do not substitute maternal high-dose supplementation for direct infant supplementation without clear evidence of adequacy 2
• Avoid excessive supplementation, though toxicity is rare at recommended doses 4