Laboratory Medicine Program

Vitamin D, 25-hydroxy
(25-hydroxycholecalciferol, 25-OH-D)

Clinical Decription:
As calciferol (Vitamin D) enters the circulation, it is metabolized to several forms, the major of these being 25-hydroxycalciferol (25-OH-D). The first step in the metabolism of vitamin D, 25 hydroxylation, occurs mainly in the liver. Only a small amount of 25-OH-D is metabolized in the kidney to other dihydroxyvitamin D metabolites in man. Since 25-OH-D is the predominant circulating form of vitamin D in the normal population, it is considered to be the most reliable index of vitamin D status.

Method: Chemiluminescent Microparticle Immunoassay

Component Tests Used: n/a

Reference Ranges Used:
<25 nmol/L Severe Deficiency. 25-60 nmol/L mild to moderate Deficiency. 61-200 nmol/L Optimum Levels. >200 nmol/L Possible Toxicity.

Specimen Type: Serum
Volume: 3 mL (minimum: 1 mL)

Shipping: 4C

Special Instructions: Centrifuge and aliquot sample.

Testing Schedule(s): Monday through Friday.

Turnaround Time: 3 days

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For more information, call 416.340.5227 or 1.866.865.5227

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