Conclusions
In summary, episodes of hypercalcemia and hypercalciuria are common events with calcium and vitamin D supplementation; they are unrelated to vitamin D dose or serum 25(OH)D level. Whether they are caused by calcium alone or by the combination of calcium with vitamin D remains uncertain. Further investigation is needed to better define individuals who are likely to develop hypercalciuria and hypercalcemia, but a high baseline 24-hour urine calcium level is one predictor of hypercalciuria. Before the start of calcium and vitamin D supplementation, it is advisable to measure blood and urine calcium levels and to perform a follow-up measurement within 3 months.