Vitamin D

Vitamin D status

• Vitamin D sufficiency – 20 to 100 ng/mL (50 to 250 nmol/L)
• Vitamin D insufficiency – 12 to 20 ng/mL (30 to 50 nmol/L)
• Vitamin D deficiency – <12 ng/mL (<30 nmol/L)

• Newborn: 8 - 21 ng/mL
• Children: 17 - 54 ng/mL
• Adults: 10 - 55 ng/mL
  

Evaluation:

• 25-OH Vitamin D as this approximates body stores (1,25-dihydroxy vitamin D is the physiologically active form - not good for determining deficiency status)
  
• Serum calcium
• Phosphorus
• Alkaline phosphatase
• PTH
• Radiographic evaluation for rickets should be performed if the child is young (eg, <3 years of age) or if there is a high clinical suspicion of rickets i.e. risk factors or physical signs

Treatment:

• Infants <12mo: 2000 international units (50 micrograms) daily for 6 to 12 weeks, followed by maintenance dosing of at least 400 international units (10 micrograms) daily.
  
• Preparations of vitamin D2 are Calcidol or Drisdol oral solution, which provide 8000 international units/mL (200 micrograms/mL).
• Children ≥12mo: 2000 international units (50 micrograms) daily for 6 to 12 weeks, followed by maintenance dosing of 600 to 1000 international units (15 to 25 micrograms) daily.
  
• An alternative approach is to treat with 50,000 international units (1250 micrograms) once a week for six weeks, followed by maintenance dosing.
  
• The Weekly regimen total dose of vitamin D is higher but has been shown to be safe and effective in several trials
  
• Obese pts or those with malabsorptive diseases or meds that impact vitamin D metabolism, use higher replacement doses (2-3x higher e.g. up to 6000 IU [150 micrograms] daily), followed by higher maintenance dosing
  
• Cystic Fibrosis may require even higher doses
  

• Children ≥12mo - 12yo: 3000 to 6000 international units (75 to 150 micrograms) daily
• Children ≥12yo: 6000 international units (150 micrograms) daily
• Treat for for 12 weeks, Then follow up labs for efficacy and risk of hypercalcemia, followed by maintenance dosing

• Calcium replacement (to prevent hypocalcemia): Give 30 to 75 mg/kg/day of elemental calcium in divided doses BID or TID
• Continued for 2-4wks or until vitamin D doses are at maintenance levels (600 to 1000 IU daily)

Follow up:

• Low 25OHD concentrations with biochemical changes such as elevated alk phos or PTH, but without rickets, Monitored more frequently to ensure treatment adherence
• Check serum 25OHD and labs after 6-8wks of  initial therapy
• Recheck after several months of maintenance therapy
• Then check annually or prn.

1. Harriet Lane
2. Update on vitamin D: position statement by the Scientific Advisory Committee on Nutrition 2007
3. World Wide Web
4. Journal Pediatrics