https://pubmed.ncbi.nlm.nih.gov/30611908/
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Extensive study supports the safety of vitamin D supplementation at doses ranging from 5,000 IU to 50,000 IU.
Daily oral dosing of vitamin D3 using 5,000 to 50,000 international units a day in long-term hospitalized patients: insights from a seven year experience, Dayton and Cincinnati, Ohio.
Vitamin D3 is a hormone produced in the skin in amounts estimated up to 25,000 international units (IU’s) a day by the action of UVB radiation. Vitamin D deficiency is common with lack of adequate sun exposure to the skin. Moreover, vitamin D is present in very few food sources.
Deficiency is strongly linked to an increased risk of multitude of diseases, several of which have historically been shown to improve dramatically with either adequate UVB exposure to the skin or with oral supplementation with vitamin D.
These diseases include: Asthma, psoriasis, rheumatoid arthritis, rickets and tuberculosis.
All patients [in our hospital] have been routinely screened on admission for vitamin D deficiency since July 2011.
They have been offered supplementation to either correct or prevent deficiency. We have admitted over 4,700 patients (vast majority agreed to supplementation) 5,000 or 10,000 IUs/day (125 micrograms or 250 micrograms). Due to disease concerns, a few agreed to 20,000 to 50,000 IUs/day (500 micrograms to 1,250 micrograms or 1.25mg).
There have been no cases of vitamin D3 induced hypercalcemia or any adverse events attributable to vitamin D3. Three patients with psoriasis marked clinical improvement using 20,000 to 50,000 IUs/day.
Summary: Long-term supplementation with vitamin D3 in doses ranging from 5,000 to 50,000 IUs/day appears to be safe.
Conclusion: Daily oral intake of vitamin D3 ranging from 5,000 IU/d to 60,000 IUs/day for several years was well tolerated and safe in both our patients and staff.