Vitamin D, 25-hydroxy

Test/Range/Collection

Vitamin D, 25-hydroxy, serum or plasma (25[OH]D)

20–50 ng/mL

[50–125 nmol/L]

SST or green

$$$

Physiologic Basis

The vitamin D system functions to maintain serum calcium levels. Vitamin D is a fat-soluble steroid hormone. Two molecular forms exist: D3 (cholecalciferol), synthesized in the epidermis, and D2 (ergocalciferol), derived from plant sources. To become active, both need to be further metabolized. Two sequential hydroxylations occur: in the liver to 25(OH) D and then, in the kidney, to 1,25[OH]2D.

Besides consequences for bone health, vitamin D deficiency reportedly is associated with a number of conditions such as cardiovascular disease, autoimmunity and cancer; however, evidence-based cause-and-effect relationships have not been established.

Interpretation

Increased in: Heavy milk drinkers (up to 64 ng/mL), vitamin D intoxication, sun exposure.

Decreased in: Dietary deficiency, malabsorption, rickets, osteomalacia, biliary and portal cirrhosis, nephrotic syndrome, renal failure, inadequate sun exposure, advanced age (> 70), primary hyperparathyroidism. Drugs: phenytoin, phenobarbital.

Comments

Serum or plasma total 25(OH)D is an integrated marker of vitamin D status, incorporating endogenous synthesis from solar exposure, dietary intake, fortified products and/or supplements.

There is no universal or strong evidence-based consensus on the appropriate level of 25(OH)D. However, according to a 2011 US Institute of Medicine Report, a 25(OH)D level of 20–30 ng/mL is all that is needed for bone and general health, and nearly everyone (97.5%) in the general population is in that range. A 25(OH)D level above 30 ng/mL has not been consistently associated with increased health benefits, and, in fact, risks have been identified for outcomes at levels above 50 ng/mL.

Routine screening for vitamin D deficiency is not necessary. Patients with the following conditions should be considered for testing: osteoporosis, osteomalacia, malabsorption, liver disease, pancreatic insufficiency, chronic kidney disease, COPD, bariatric surgery, cancer, bedridden or home-bound, obesity, taking anticonvulsants or long-term glucocorticoids, atraumatic fractures, elderly (> 70 years old), and chronic inflammatory conditions.

Vitamin D toxicity can occur after taking excessive doses of vitamin D, a condition that is manifested by hypercalcemia, hyperphosphatemia, soft tissue calcification, and renal failure.

Bikle DD. Vitamin D metabolism, mechanism of action, and clinical applications. Chem Biol 2014;21:319.  [PMID: 24529992]

LeBlanc E et al. Screening for vitamin D deficiency: systematic review for the U.S. Preventive Services Task Force Recommendation [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2014 Nov.  [PMID: 25521000]

Vitamin D, 25-hydroxy is a sample topic from the Guide to Diagnostic Tests.

To view other topics, please or purchase a subscription.

Anesthesia Central is an all-in-one web and mobile solution for treating patients before, during, and after surgery. This collection of drug, procedures and test information is derived from Davis’s Drug, MGH Clinical Anesthesia Procedures, Pocket Guide to Diagnostic Tests, and MEDLINE Journals. Learn more.

Citation

* When formatting your citation, note that all book, journal, and database titles should be italicized* Article titles in AMA citation format should be in sentence-case
TY - ELEC T1 - Vitamin D, 25-hydroxy ID - 619068 Y1 - 2017 PB - Guide to Diagnostic Tests UR - https://anesth.unboundmedicine.com/anesthesia/view/GDT/619068/all/Vitamin_D__25_hydroxy ER -