Name of the Test:  Vitamin D  1, 25 dihydroxy

Alias   Names : Calcitriol   (Vitamin D, 1,25-dihydroxy), D,1-25 dihydroxy, Vitamin (Vitamin D, 1, 25-dihydroxy)

Clinical Applications:

Vitamin D3 is produced by the skin endogenously .Vitamin D2 is primarily a plant product and is in many nutritional vitamin supplements.  Both Vitamin D2 and D3 are biologically active. Vitamin D is converted into 25 hydroxy vitamin D      (25-OH D) in the liver. In kidney, it is converted into 1,25 dihydroxy vitamin D, which is biologically active.1,25-dihydroxy vitamin D is the most potent vitamin D metabolite. It stimulates calcium absorption in the intestine and its production is tightly regulated through concentrations of serum calcium, phosphorus, and parathyroid hormone.1,25-Dihydroxy vitamin D levels may be high in primary hyperparathyroidism and in physiologic hyperparathyroidism secondary to low calcium or vitamin D intake. Some patients with granulomatous diseases (e.g. sarcoidosis) and malignancies containing nonregulated 1-alpha hydroxylase in the lesion may have elevated 1, 25-dihydroxy vitamin D levels and hypercalcemia.   1, 25-dihydroxy vitamin D levels are decreased in hypoparathyroidism and in chronic renal failure.


1, 25 dihydroxy vitamin D from serum sample is purified by an immunoaffinity column following delipidation. The purified preparation is incubated with an antibody and biotinylated 1, 25 dihydroxy vitamin D. A competitive immunoassay was performed using biotinylated vitamin D 1, 25 dihydroxy with an antibody to vitamin D 1,25 dihydroxy. The concentration of 1, 25 dihydroxy is inversely related to the color developed and measured at 450 nm.

Test information:

Specimen requirements: 2 ml of serum or plasma (0.6 ml minimum )

Shipping requirements: Ship the samples frozen or in ice packs. Shipping samples at room temperature is not recommended.

Turnaround time: 2 days (setup every Tuesday )

Reference Range:   15 – 80 pg /ml


  1. Cantorna MT, Zhu Y , Froicu M,Wittke A ( 2004) Vitamin D status, 1,25 –dihydroxyvitamin D3 and the immune system. Amer J Clin Nutr 80: 1717 -1720.
  2. DeLuca HF (1993) Vitamin D. Nutr Today 28: 6 – 11.

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