Vitamin D, 25-Hydroxy, LC/MS-MS

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Turnaround Time: 4 - 10 days
CPT Code:


Test Type: 1 mL Serum (preferred) or plasma


25-Hydroxy vitamin D is used to measure vitamin D status; it includes results for total 25-hydroxy vitamin D2 and 25-hydroxy vitamin D3. This 25-hydroxy vitamin D assay and the alternative immunoassay test (Vitamin D, 25-Hydroxy [081950]) are both CDC-certified for accuracy.1

The biological function of vitamin D is to maintain normal levels of calcium and phosphorus absorption. 25-Hydroxy vitamin D is the storage form of vitamin D. Vitamin D assists in maintaining bone health by facilitating calcium absorption. Vitamin D deficiency can also cause osteomalacia, which frequently affects elderly patients. Vitamin D from sunshine on the skin or from dietary intake is converted predominantly by the liver into 25-hydroxy vitamin D, which has a long half-life and is stored in the adipose tissue. The metabolically active form of vitamin D, 1,25-di-hydroxy vitamin D, which has a short life, is then synthesized in the kidney as needed from circulating 25-hydroxy vitamin D. The reference interval of greater than 30 ng/mL is a target value established by the Endocrine Society.2

1. Centers for Disease Control and Prevention (CDC). Laboratory Quality Assurance and Standardization Programs. Standardization of Measurement Procedures. Vitamin D Standardization Certification Program (VDSCP). Atlanta, Ga: CDC;2015. Available at: Accessed April 12, 2015.

2. Holick MF, Binkley NC, Bischoff-Ferrare HA, et al. Evaluation, treatment, and prevention of vitamin D deficiency: An Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011; 96(7):1911-1930. PubMed 21646368

Collection Details:

Collection Instructions:

Red-top tube, gel-barrier tube, lavender-top (EDTA) tube, or green-top (heparin) tube.

Serum or plasma must be separated from cells within 45 minutes of venipuncture. Submit serum or plasma in a plastic transport tube.

Freeze. Stable frozen for 34 months. Stable at room temperature or refrigerated for seven days.