Assessing vitamin D status

Purpose of Review: To characterize methods evaluating and to summarize studies linking various serum 25-hydroxyvitamin D [25(OH)D] concentrations with health status. Recent Findings: Elucidation of the cell-biologic mechanism of vitamin D action, and numerous clinical trials and observational studies relating vitamin D status to health and disease. Conclusion: The distinction between deficiency and insufficiency is not useful or necessary. Serum 25(OH)D values below 120 nmol/l (48 ng/ml) are associated with preventable disease and are therefore indicative of deficiency. The upper limit of the normal range can be set at 225 nmol/l (90 ng/ml), although toxicity is rare below 500 nmol/l (200 ng/ml).