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Vitamin D (25-hydroxy)

Item Value
Approval req'd? No
Available Stat? No
Test code VITMD
Performed by? Chemistry
Sendout? No
Price range $
In House Availability Daily, Mon - Fri
Principle This method quantifies the sum of 25-OH Vitamin D3 and 25-OH Vitamin D2 using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).
Interpretation This test is useful for the diagnosis of vitamin D deficiency and hypervitaminosis D. It can also be used in the differential diagnosis of causes of rickets and osteomalacia or monitoring vitamin D replacement therapy.

A deficiency in the vitamin D concentrations is linked to a variety of health problems including bone disorders, cardiovascular disease and cancer 1. Vitamin D is derived from dietary ergocalciferol (Vitamin D2, plants) or cholecalciferol (Vitamin D3, animals) and by the conversion of 7-dihydrocholesterol to Vitamin D3 in the skin upon ultraviolet exposure. In the liver, Vitamin D2 and D3 are 25-hydroxylated to form 25-OH Vitamin D. 25-OH-Vitamin D represents the main body stores of Vitamin D. In the kidneys, a fraction of circulating 25-OH-Vitamin D is converted to its active metabolite 1,25-dihydroxy vitamin D. Subjects who get an insufficient amount of sunlight or have dietary deficiencies or malabsorption will have low concentrations of 25-OH Vitamin D.
Container type red top (plain) or gold top gel tube
Amount to Collect 2 mL
Sample type serum
Min. Volume 0.25 mL
Units ng/mL
Normal range
Deficiency: < 20 ng/mL
Insufficiency: 20 – 29 ng/mL
Optimum Level: 30 – 80 ng/mL
Possible Toxicity: > 80 ng/mL*

There is no standardized suggested reference range established for vitamin D. The Endocrine Society recommends a reference range (optimum level) of 30 – 100 ng/mL, while the Institute of Medicine (IOM) recommends a reference range (optimum level) of 20 – 50 ng/mL for the general healthy population. The IOM further clarifies this range by stating that values in the range of 20 – 50 ng/mL may be insufficient in certain patient populations. There is no known benefit to values > 50 ng/mL.

* A vitamin D level of 80 ng/mL is the lowest reported level associated with toxicity in patients without primary hyperthyroidism who have normal renal function. Most patients with toxicity have levels > 150 ng/mL.
Synonyms Vitamin D; 25-Hydroxy D2, 25-Hydroxy D3; 25-Hydroxycholecalciferol; 25-Hydroxyergocalciferol, 25-OH Vitamin D; Calcidiol; Calcifediol, D2, D3
Stability After separation from cells - RT: 24 hours; refrigerated: 1 week; Frozen: 6 months
Interferences Approximately 23% of children less than 1 yr old form significant concentrations of C-3 epimers of 25-OH Vitamin D 6. This method cannot differentiate Vitamin D from its C-3 epimers which can lead to overestimation of 25-OH Vitamin D levels in infants.
Turn around times 3 - 5 days
Additional information The reference range for total 25-OH Vitamin D (30 - 80 ng/mL) is based on 25-OH Vitamin D correlation with physiological parameters that include parathyroid hormone concentration and calcium absorption 2-5. The range is not based on the distribution of levels in an apparently healthy population. The exact 25-OH Vitamin D level reflecting optimal body stores is currently unknown.
References 1) Stechschulte SA, Kirsner RS and Federman DG. Vitamin D: bone and beyond, rationale and recommendations for supplementation. Am J Med. 2009;122(9):793-802.

2) Hollis BW. Circulating 25-hydroxyvitamin D levels indicative of vitamin D sufficiency: implications for establishing a new effective dietary intake recommendation for vitamin D. J Nutr. 2005;135:317-322.

3) Holick MF. Vitamin D deficiency: what a pain it is. Mayo Clin Proc. 2003;78:1457-1459.

4) Malabanan A, Veronikis IE and Holick MF. Redefining vitamin D insufficiency. Lancet. 1998;351:805-806.

5) Plotnikoff GA and Quigley JM. Prevalence of severe hypovitaminosis D in patients with persistent, nonspecific musculoskeletal pain. Mayo Clin Proc. 2003;78:1463-1470.

6) Singh RJ, Taylor RL, Reddy GS and Grebe SKG. C-3 Epimers can account for a significant proportion of total circulating 25-hydroxyvitamin D in Infants, complicating accurate measurement and interpretation of vitamin D status. J Clin Endocrinol Metab. 2006;91(8):3055-61.
CPT coding 82306
Last Updated 7/24/2015 5:26:59 PM
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