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Test Code B12 Vitamin B12, Serum or Plasma

Important Note

Patient Preparation:

A fasting specimen of 6-8 is preferred  (but not requried) for this test.

Ask patients if they have received a vitamin B12 injection within the last 2 weeks. Patient results will not reflect deficiency or malabsorption after recent B12 injection. If patient has received an injection within the past 2 weeks, this test should not be ordered.

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

Additional Codes

Epic Order Code: LAB67
Sunquest Order Code: B12

Specimen Required

Container Type:


Inpatient: Mint

STAT: Mint

Outpatient: Gold

Acceptable: Red Top or Green Lithium Heparin.


Optimal Collection Volume: 

A full tube is optimal for all blood draws.  Not only does it give the correct ratio of anticoagulant or clot activator to blood, a full tube allows for efficient automated testing and provides residual sample for any repeat, add on or reflex tests.   Please note: In most cases, multiple test orders requiring the same tube type may be combined in one tube.   Do not draw a separate tube for each test.   For exceptions where a test has a larger sample volume requirement, it will be noted in this section.


The approximate volume of blood needed for this test is 1.0 mL of blood (0.5 ml of serum or plasma).

Collection Instructions:

Gently invert sample 5-6 times after collection.

Processing Instructions: 

1. Allow serum sample to clot for 30 minutes.

2. Centrifuge specimen within 2 hours of collection.

3. Specimen tubes without a gel barrier should have the serum or plasma aliquoted to a false bottom container after centrifugation.

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

Useful For

This assay is used as the investigation of nutritional and macrocytic anemias caused by a deficiency of vitamin B12.

Method Name

Electrochemiluminescence Immunoassay

Stability Information

Specimen Type Temperature Time
Serum/Plasma Refrigerated 7 days
  Ambient  2 hours
  Frozen  2 months

Rejection Due To

Hemolysis Mild OK; Moderate Reject; Gross Reject
Lipemia Mild OK; Moderate OK; Gross Reject
Icterus Mild OK; Moderate OK; Gross Reject
Other N/A


Post Processing Specimen Type


Preferred: Serum

Alternate: Plasma

Specimen Minimum Volume

Collecting minimum volumes can result in a need for sample recollection, and/or a delay in results. Minimum volumes are subjective and cannot account for all aspects of specimen and testing needs. Refer to the Specimen Required section for optimal volumes for laboratory specimens. Contact the Bronson Laboratory if complex collection exceptions occur that require more information.


Minimum Volume: 1 mL whole blood, 0.5 mL serum or plasma

Performing Laboratory

Bronson Laboratory, Chemistry - Paw Paw

Day(s) Performed


Reference Values

 Test ID   Reference Range    Units      
B12 211-946 pg/mL

LOINC Code Information


CPT Code Information


Sample Retention Time

7 days