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Test Code B12 Vitamin B12, Plasma

Specimen Type

Preferred: Plasma

Acceptable: Serum


Plasma: Li-Heparin (Mint Green or Dark Green)

Serum: Red Top tube or Gold STT

Preferred Volume

3 mL

Offsite Collection Instructions

1. Fasting (8-14 hours) specimens are recommended. 

2. Serum gel tube should be centrifuged within 2 hours of collection.

3. Red-Top tube or Dark Green Li-Heparin tube should be centrifuged and aliquot within 2 hours of collection.


UCMC Collection Instructions

1. Fasting (8-14 hrs) specimens are recommended.  Protect sample from light.

2. Samples should be spun within 2 hours of collection.



Turnaround Time

4 hrs

STAT Availability

Not Available

Test Usage

Useful as an aid in the investigation of macrocytic anemia and workup of deficiencies seen in megaloblastic anemias.

Test Methodology

Electrochemiluminescence Immunoassay (ECLIA)

Additional Information

A normal serum concentration of vitamin B12 does not rule out tissue deficiency of vitamin B12. The most sensitive test for vitamin B12 deficiency at the cellular level is the assay for MMA. If clinical symptoms suggest deficiency, measurement of MMA and homocysteine should be considered, even if serum vitamin B12 concentrations are normal.

CPT Code


Test Includes

Quantitative determination of vitamin B12 in plasma or serum

Critical Results


Test Limitations

In patients receiving therapy with high biotin doses (i.e. > 5 mg/day), no sample should be taken until at least 8 hours after the last biotin administration.
Patients taking vitamin B12 supplementation may have misleading results.

Reference Range

240-900 pg/mL

Minimum Volume

0.5 mL

Fee Code