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Test Code B12 or LAB67 Vitamin B12, Serum or Plasma

Important Note

Patient Preparation:

A fasting specimen of six to eight hours is preferred but not required for this test.

Ask patients if they have received a vitamin B12 injection within the last two weeks. Patient results will not reflect deficiency or malabsorption after a recent B12 injection. This test should not be ordered if the patient has received an injection within the past two weeks.

For 12 hours before this test, do not take multivitamins or dietary supplements containing biotin (vitamin B7), commonly found in hair, skin, and nail supplements, and multivitamins. Biotin can interfere with many immunoassay tests.

Specimen Requirements

Container Type:

Optimal: Gold or Mint*

*For STAT requests

Acceptable: Red or Green
Optimal Collection Volume: 

4.5mL; full tube
Minimum Volume:
  • Adults: 1 mL whole blood
  • Neonates: 1 microtainer (400-600 uL)
Collection Instructions:

Gently invert the sample 5-6 times after collection.
Specimen Transport:

Refrigerate
Processing Instructions: 

1. If serum, allow the specimen to clot for 30 minutes.

2. Centrifuge specimen within 2 hours of collection.

3. After centrifugation, specimen tubes without a gel barrier should have the serum or plasma aliquoted to a false bottom container.

4. Keep serum or plasma refrigerated until testing can be performed.

Specimen Stability

Specimen Type Temperature Time
Serum* Refrigerated 7 days
Room Temperature 2 hours
Frozen 2 months

*Note: Heparinized plasma in gel separator tubes is less stable than serum and is only suitable for add-on testing up to 2 days following sample collection.

Specimen Rejection Criteria

Hemolysis Mild OK; Moderate Reject; Gross Reject
Lipemia Mild OK; Moderate OK; Gross Reject
Icterus Mild OK; Moderate OK; Gross Reject
Other Quantity not sufficient

Useful For

This assay is used to investigate nutritional and macrocytic anemias caused by a deficiency of vitamin B12.

Methodology

Roche Cobas - Electrochemiluminescence immunoassay

Reference Ranges

232-1245 pg/mL

Interpretive

B12 - Clinical & Interpretive: Vitamin B12 Assay, Serum (mayocliniclabs.com)

Day(s) Performed

24/7

Expected TAT

Same day

Performing Laboratory

Bronson Laboratory, Chemistry - Kalamazoo

Sample Retention Time

7 days

CPT Code

82607

LOINC Code

2132-9