Measuring Serum Vitamin D is Problematic

Data suggest that vitamin D status is suboptimal among many adults (). Accordingly, some experts advise that clinicians measure . . .

Data suggest that vitamin D status is suboptimal among many adults (Journal Watch May 14 1999). Accordingly, some experts advise that clinicians measure patients' serum 25-hydroxyvitamin D (25-OHD) levels to guide supplementation. How accurate are such measurements? Researchers approached this question in several ways:

Serum from 59 postmenopausal women was sent to either of two national laboratories. In one laboratory, nearly all levels were higher than 30 ng/mL; in the other, nearly all levels were lower than 30 ng/mL.
Serum from each of 10 healthy young adults was sent to six different commercial and research laboratories. One lab measured 25-OHD levels using the gold standard method (high-pressure liquid chromatography); the other five us…

Reviewing Author

Allan S. Brett, MD