Retrospective psychiatric patients in the USA finding that prolonged daily oral intake of vitamin D3 from 5,000 to 10,000 IU/day was safe. There was no evidence for hypercalcemia, renal failure, calcium crystal formation, nephrolithiasis. or undetectable parathyroid hormone concentrations (previously reported), and urine calcium concentrations were normal.
Repas et al., 12 May 2023, peer-reviewed, 6 authors.