2.5 Safety Considerations, High Dosages Elevate 25(OH)D with No Adverse Effects There are no observed adverse effects at vitamin D2 or D3 doses of 1800 IU/d in infants (1). In the event of hypervitaminosis D, hypercalciuria and or hypercalcemia could occur. Sustained hypercalcemia could manifest as failure-to thrive, anorexia, irritability, nephrocalcinosis and its effects, and the remote possibility of cardiac arrhythmias. In one published study where infants received approximately 1200 IU of vitamin D per day (D2 supplements and D3 formula) (43), and in a pilot coordinated Dr. Taback (Univ. Manitoba) and the applicants (see CV module, CDA grant) where infants received 2000 IU/d of vitamin D3, no hypercalcemia or hypercalciuria was noted. In the later trial, PTH data are not yet available and this dose of vitamin D3 results in 25(OH)D well above 75 to 80 nmol/L (199 nmol/L, n=4). While too small to calculate SD, this study suggests that the required intake of vitamin D3 is likely below 2000 IU/D.