Normal 24-hour urine calcium concentrations after long-term daily oral intake of vitamin D in doses ranging from 5000 to 50,000 international units in 14 adult hospitalized psychiatric patients

Abstract

Many controversies exist regarding vitamin D₃ supplementation. These include not only diseases that are responsive to vitamin D supplementation, but also the long-term safety of prolonged daily oral vitamin D₃ intake above 4000-10,000 International Units (IU). In particular, supplementation levels that do not result in adverse events, and the upper limits of safe serum 25-hydroxyvitamin D (25OHD) concentrations. Adverse reactions reported to occur with excessive vitamin D intake include hypercalcemia, renal failure, calcium crystal formation, undetectable parathyroid hormone concentrations, and hypercalciuria, all of which are reported to be reversible. To address the long-term safety of vitamin D supplementation, we previously reported data from patients in our hospital who have been voluntarily supplemented with vitamin D₃ ranging from 5,000 to 10,000 IU/day since July 2011 as a standard of care for the prevention and treatment of vitamin D deficiency. Historically 90% of patients have agreed to daily supplementation, with most taking 10,000 IU/day. These data indicate no evidence for hypercalcemia, renal failure, calcium crystal formation, nephrolithiasis. or undetectable parathyroid hormone concentrations in patients taking 5000 or 10,000 IU/day for extended periods of time. As another measure for potential vitamin D toxicity, we retrospectively assessed 24-hour urine calcium excretion in 14 individuals on long-term daily oral vitamin D intake ranging from 5000 to 50,000 IU/day to further assess the safety of supplementation using these doses. This included patients taking either 5000 (4), 10,000 (9), or 50,000 (1) IU/day. Time on supplementation ranged from 10 to 102 months. A patient taking 400 IU/day and getting frequent sun exposure was also included. All fifteen 24-hour urine calcium measurements were normal. The current findings complement our experience with over 7000 patients in the past 13 years, indicating that prolonged daily oral intake of vitamin D₃ ranging from 5000 to 10,000 IU/day is safe.

Keywords: COVID-19; Deficiency; Hypercalcemia; Hypercalciuria; Safety; Vitamin D.