VITAMIN D (25-HYDROXY) - serum

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Specimen: 5 mL blood in plain tube.

Method: Immunoassay.

Reference Interval: 40-160 nmol/L.

Application: Investigation of suspected rickets and osteomalacia (eg malabsorption, dietary deficiency). Investigation of suspected vitamin D toxicity (hypercalcaemia, nephrocalcinosis, overdose).

Interpretation: Although 25-hydroxycholecalciferol is usually reliable for the diagnosis of abnormal vitamin D states, in a few instances (eg sarcoidosis) 1,25-dihydroxycholecalciferol alone is abnormal.

Reference: Audran M. Mayo Clin Proc 1985; 60: 851-866.

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