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...
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.
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
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Holick MF. Vitamin D deficiency. N Engl J Med. 2007 Jul 19;357(3):266-81. Available at: https://pubmed.ncbi.nlm.nih.gov/17634462
Sanders KM, Stuart AL, Williamson EJ, Simpson JA, Kotowicz MA, Young D, Nicholson GC. 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. Available at: https://pubmed.ncbi.nlm.nih.gov/20460620
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. Available at: https://pubmed.ncbi.nlm.nih.gov/16549491