Vitamin D, 25-Hydroxy
Label Mnemonic: VITD25
Epic Lab Code: LAB535
Downtime Form: A-1a Doctor/Provider Orders - Pathology Core and Specialty Care Nursery
6240 RCP
Collection Medium:
Plasma Separator Tube 4.5 mL
3 mL whole blood from light green top tube or TWO Microtainer® devices for pediatric patients.
Turn Around Time:
1 hour (upon receipt in laboratory)
Reference Range:
Reference range in Epic: 20-80 ng/mL

Deficiency: Less than 20 ng/mL
Borderline: 20-29 ng/mL
Optimum level: 30-80 ng/mL
Possible toxicity: > 150 ng/mL
Interpretive Data:
This is the appropriate screening test for routine assessment of vitamin D nutritional status. This assay accurately quantifies the sum of 25-hydroxyvitamin D3 and 25-hydroxyvitamin D2. 25-Hydroxyvitamin D reference ranges are a controversial topic, with some authorities suggesting optimal concentrations should be 30 ng/mL or higher based on correlations of 25-hydroxyvitamin D plasma concentrations with physiological parameters such as parathyroid hormone or calcium concentrations.

Endocrine Society, Institute of Medicine (IOM), and World Health Organization (WHO) guidelines designate 25-hydroxyvitamin D plasma concentrations below 20 ng/mL as deficient, based on increased frequency of adverse outcomes (e.g., osteoporotic fractures). However, optimal 25-hydroxyvitamin D concentrations greater than 20 ng/mL may be considered for specific disease conditions. 25- Hydroxyvitamin D concentrations should be interpreted in context of clinical history and physical examination along with other laboratory studies, if indicated. For workup of hypercalcemia, vitamin D status in renal failure patients, and certain malignancies, "Vitamin D (1,25- dihydroxy)" may be indicated.
This assay may be significantly impacted by high-dose biotin (>5 mg dose) taken within previous 12 hours. High concentrations of biotin may lead to falsely decreased results. These concentrations may be found in patients taking over-the-counter supplements with biotin content much higher than nutritional requirements for biotin. Specimens should not be collected until at least 12 hours after the last dose.

Endocrine Society Clinical Guidelines. J Clin Endocrinol Metab 96: 1911-1930, 2011.
Holick MF, NEJM 357: 266-281, 2007.
Krasowski MD, Am J Clin Pathol 136: 507-514, 2011.
Vieth R. Am J Clin Nutr 69:842-856, 1999.
Wharton B, Bishop N. Lancet 362:1389-1400, 2003.

This test is also performed in the Iowa River Landing (IRL) clinical laboratory (for specimens drawn at that site).
Test Limitations:
Avoid grossly hemolyzed specimens.
Electrochemiluminescence Immunoassay, Multiplex flow immunoassay
CPT Code:
See also:
Vitamin D (1,25 Dihydroxy), Serum
See Additional Information:
Biotin Interference with Immunoassays