1,25-dihydroxy vitamin D (1,25DHD) is the active form of vitamin D, produced primarily by the kidney by hydroxylation of 25-hydroxy vitamin D. 1,25DHD is the form of vitamin D that stimulates resorption of calcium from bone, intestinal absorption and renal reabsorption.
NB. 1,25DHD should not be used to determine vitamin D status; 25-hydroxy vitamin D is the best marker for this purpose.
Indications for 1,25DHD are limited. Measurement may be useful in the investigation of possible vitamin D-dependent rickets and in patients with hypercalcaemia to investigate possible excess 1,25DHD production e.g. granulomatous diseases (sarcoidosis, TB or lymphoma).
Sample Requirements and Reference Ranges
|Minimum volume||2 mL|
|Reference range||20 - 120 pmol/L|
|Turnaround time||35 days|