What you need to know about VITAMIN D

Most people will need supplements. We don't get much vitamin D from the sun these days due to sunscreens, staying indoors, etc....
Mahitab Hany, BS Pharm, PGDipClinPharm, PGDipClinNutrition

Overview

Now that so many more people are taking vitamin D, some are asking how much vitamin D is too much. Explain that vitamin D doses vary widely and toxicity is rare...

Management

Treat and prevent deficiency

To prevent deficiency, recommend 1000 to 2000 IU/day of vitamin D for adults and 400 IU/day for infants and children. Most people will need supplements. We don't get much vitamin D from the sun these days due to sunscreens, staying indoors, etc. Diet usually isn't enough, either. Very few foods contain vitamin D and milk contains only 100 IU per cup. Higher doses are needed to maintain adequate levels in some patients or to treat a deficiency.

  • TO TREAT DEFICIENCY in adults, vitamin D deficiency can lead to osteomalacia in adults. Symptoms of vitamin D deficiency include bone pain and muscle weakness.
    • Prescribe 50,000 IU (1.25 mg)/week of vitamin D2 or D3 orally for 6 to 12 weeks then recheck levels.
    • Make sure patients understand this is a weekly dose, not a daily dose.
  • TO TREAT DEFICIENCY in children, initial dose is 2000 IU/day, or 50,000 IU once weekly, for six weeks.
    • Maintenance dose is once vitamin D level is > 30 ng/mL, reduce to 400 to 1000 IU/day (0 to one year of age) or 600 to 1000 IU/day (one to 18 years of age).

Tell patients it's okay to consume milk and multivitamins while on this weekly vitamin D dose. Optimal blood levels of 25-hydroxyvitamin D for bone health are at least 30 ng/mL. Normal levels can reach 100 ng/mL. Increasing the dose by 1000 IU/day increases blood levels about 7 to 10 ng/mL.

NPS-adv

Toxicity

Hypercalcemia, and hyperphosphatemia usually don't occur until vitamin D levels exceed 150 ng/mL. Toxicity can occur with excessive doses such as 40,000 IU/day for one month in infants and 50,000 IU/day for several months in adults. Warn parents not to use vitamin D liquids dosed as 400 IU/DROP. Giving one dropperful or 1 mL by mistake can deliver 10,000 IU/day. FDA will force companies to provide no more than 400 IU per dropperful. Patients sometimes ask if they can take vitamin D once a week or month for maintenance.

  • Explain that it's okay to take 14,000 IU once a WEEK or 50,000 IU once a MONTH instead of 2000 IU/day.
  • Encourage using D3 cholecalciferol (Davalindi 1000iu) since it's more potent than D2 ergocalciferol (Ossofortin), BUT vitamin D2 is also effective and okay to use.

References

  1. Holick MF. Vitamin D deficiency. N Engl J Med. 2007 Jul 19;357(3):266-81.
  2. Sanders KM, Stuart AL, et al. Annual high-dose oral vitamin D and falls and fractures in older women: a randomized controlled trial. JAMA. 2010 May 12;303(18):1815-22.
  3. Vieth R. Critique of the considerations for establishing the tolerable upper intake level for vitamin D: critical need for revision upwards. J Nutr. 2006 Apr;136(4):1117-22.