A study found that 66% of the 1,25 dihydroxyvitamin D tests were ordered in error, and that in these cases, 25-OH vitamin D was the intended test.
As laboratorians know, 25-OH vitamin D is most useful in nutritional assessment, primarily due to its longer half-life of approximately 3 weeks. 25-OH vitamin D is elevated with vitamin D intoxication and decreased with malabsorption, nutritional deficiency, and in liver disease. Conversely, the circulating half-life of 1,25 dihydroxyvitamin D is relatively short (4–6 hours), limiting utility for overall vitamin D assessment,” they explained. However, the 1,25 dihydroxyvitamin D test can be useful for diagnosis of renal dysfunction, in conjunction with parathyroid hormone.
Steering Doctors to the Right Vitamin D Test