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Test Code 25VITD Vit D 25 Hydroxy, LAB535


Direct competitive chemiluminescence immunoassay (CLIA) for quantitative determination

Performing Laboratory

St. Luke's Hospital Cedar Rapids

Specimen Requirements


Preferred: Gold-top serum gel tube(s) 

Acceptable:  Plain, red-top tube(s)

Specimen Volume: 250 uL of serum

Stability:  If the assay is performed within 120 hours (5 days) of sample collection, the samples should be kept at 2-8°C; otherwise they should be stored frozen (-20°C or below).

Collection Instructions:

1. Fasting (preferred but not required).

2. Centrifuge immediately and separate from cells within 1 hour of draw.

3. Label specimen appropriately (serum).

4. Forward promptly.

Additional Information:

1. Grossly hemolyzed specimens should be recollected.

2. Lipemic samples should be ultracentrifuged before testing.

3. If there is a delay in transport of >5 days or if mailing time exceeds 5 days, spin down, remove serum from cells and freeze immediately in plastic vial. Send specimen frozen.

Reference Values

Severe deficiency: <10 ng/mL

Mild to moderate deficiency: 10-29 ng/mL

Optimum levels: 30-100 ng/mL

Toxicity possible: >100 ng/mL

Day(s) Test Set Up

Monday through Friday (days only)

Test Classification and CPT Coding


Useful For

25-Hydroxyvitamin D is the best indicator of vitamin D nutritional status and is helpful in the diagnosis of Vitamin D deficiencies.