B12 - Specimen: Vitamin B12 Assay, Serum

Test Catalog

Test Name

Test ID: B12    
Vitamin B12 Assay, Serum

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Vitamin B12 Deficiency Evaluation in Special Instructions.

Specimen Type Describes the specimen type validated for testing


Advisory Information

This test provides a measurement of serum B12 level only. If a more comprehensive workup is preferred, consider ACASM / Pernicious Anemia Cascade.


The ACASM cascade simplifies the evaluation of B12 deficiency and ensures that additional testing is performed in patients with a decreased vitamin B12 level. The cascade begins with serum B12 measurement. If the vitamin B12 level is less than 150 ng/L, intrinsic factor-blocking antibody (IFBA) testing is automatically performed. If the IFBA test is negative or indeterminate, gastrin level is evaluated. If the serum vitamin B12 level is 150 to 400 ng/L, methylmalonic acid is measured. If the methylmalonic acid is greater than 0.40 units/L, IFBA testing is performed. If the serum vitamin B12 level is above 400 ng/L, no further testing is performed. See Vitamin B12 Deficiency Evaluation algorithm in Special Instructions.

Necessary Information

Ask patients if they have received a vitamin B12 injection within the last 2 weeks. If patient has received an injection within the past 2 weeks, this test cannot be ordered.

Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 0.6 mL

Collection Instructions:

1. Serum gel tubes should be centrifuged within 2 hours of collection.

2. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.


If not ordering electronically, complete, print, and send a Benign Hematology Test Request Form (T755) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/benign-hematology-test-request-form.pdf)

Specimen Minimum Volume The amount of sample necessary to provide a clinically relevant result as determined by the Laboratory.

0.5 mL

Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected


Mild OK; Gross reject


Mild OK; Gross OK





Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperatures are also included.

Specimen TypeTemperatureTime
SerumRefrigerated (preferred)7 days
 Frozen 90 days