RESUMEN
Measurement of vitamin D levels and supplementation with oral vitamin D have become commonplace, although clinical trials have not demonstrated health benefits. The usefulness of serum 25-hydroxyvitamin D levels to assess adequate exposure to vitamin D is hampered by variations in measurement technique and precision. Serum levels less than 12 ng per mL reflect inadequate vitamin D intake for bone health. Levels greater than 20 ng per mL are adequate for 97.5% of the population. Routine vitamin D supplementation does not prolong life, decrease the incidence of cancer or cardiovascular disease, or decrease fracture rates. Screening asymptomatic individuals for vitamin D deficiency and treating those considered to be deficient do not reduce the risk of cancer, type 2 diabetes mellitus, or death in community-dwelling adults, or fractures in persons not at high risk of fractures. Randomized controlled trials of vitamin D supplementation in the treatment of depression, fatigue, osteoarthritis, and chronic pain show no benefit, even in persons with low levels at baseline.