Daily oral dosing of vitamin D3 using 5000 TO 50,000 international units a day in long-term hospitalized patients: Insights from a seven year experience https://pubmed.ncbi.nlm.nih.gov/30611908/ Dayton and Cincinnati, Ohio Vitamin D3 is a hormone produced in the skin, in amounts estimated up to 25,000 international units (IUs) a day, by the action of UVB radiation Vitamin D deficiency is common, lack of adequate sun exposure to the skin, vitamin D is present in very few food sources. Deficiency is strongly linked to increased risk for a multitude of diseases, several of which have historically been shown to improve dramatically with either adequate UVB exposure to the skin, or to 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 Offered supplementation to either correct or prevent deficiency We have admitted over 4,700 patients (vast majority agreed to supplementation) 5000 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 (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 Analysis of 418 inpatients on D3 Long enough to develop 25OHD3 blood levels less than 74.4 ng/ml, showed a mean 25OHD3 level of 118.9 ng/ml (range from 74.4 to 384.8 ng/ml) Average serum calcium level in the vit D group of 418 9.6  mg/dl Range of 8.6 to 10.7 (Normal 8.5 to 10.5) Average serum calcium level in the non vit D group of 777 Mean 25OHD3 level of 27.1 ng/ml 9.5 mg/dl Range of 8.4 to 10.7 Parathyroid hormone levels A hormone released in response to low calcium levels D3 users, 24.2 pg/ml Non D3 users, 30.2 pg/ml In summary Long-term supplementation with vitamin D3 in doses ranging from 5000 to 50,000 IUs/day appears to be safe. Conclusion Daily oral intake of vitamin D3 ranging from 5000 IU/d to 60,000 IU/d for several years was well tolerated and safe, in both our patients and staff. The mean 25OHD blood levels in our patients appear to take around 12 months to plateau on 5000 IU/d and 10,000 IU/d. The average 25OHD values Patients taking 10,000 IU/d at 12 months = 96 ng/ml Then retested at 16 months = 97 ng/ml Currently considered upper limit of normal, 100 ng/ml Conflicts of Interest The authors have no conflicts of interest to disclose. Funding This research was performed without external funding.