Clinical Information

This test is used as a second-order test in the assessment of vitamin D status, especially in patients with renal disease, or for investigation of some patients with clinical evidence of vitamin D deficiency (e.g., vitamin D-dependent rickets due to hereditary deficiency of renal 1-alpha hydroxylase or end-organ resistance to 1,25-dihydroxyvitamin D), or for differential diagnosis of hypercalcemia.  1,25-Dihydroxyvitamin D concentrations are low in chronic renal failure and hypoparathyroidism. 1,25-Dihydroxyvitamin D concentrations are high in sarcoidosis and other granulomatous diseases, some malignancies, primary hyperparathyroidism, and physiologic hyperparathyroidism. 1,25-Dihydroxyvitamin D concentrations are not a reliable indicator of vitamin D toxicity; normal (or even low) results may be seen in such cases.