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HelpTest ID B12 Vitamin B12 Assay, Serum
Useful For
Investigation of macrocytic anemia
Workup of deficiencies seen in megaloblastic anemias
Testing Algorithm
See Vitamin B12 Deficiency Evaluation in Special Instructions.
Special Instructions
Method Name
Immunoenzymatic Assay
Reporting Name
Vitamin B12 Assay, SSpecimen Type
SerumContainer/Tube:
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.
Forms: If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:
Neurology Test Request Form-General (T732) (http://www.mayomedicallaboratories.com/it-mmfiles/neurology-request-form.pdf)
Benign Hematology Test Request Form (T755) (http://www.mayomedicallaboratories.com/it-mmfiles/benign-hematology-test-request-form.pdf)
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 7 days |
| Frozen | 90 days |
Clinical Information
Vitamin B12 (cobalamin) is necessary for hematopoiesis and normal neuronal function. In humans, it is obtained only from animal proteins and requires intrinsic factor (IF) for absorption. The body uses its vitamin B12 stores very economically, reabsorbing vitamin B12 from the ileum and returning it to the liver; very little is excreted.
Vitamin B12 deficiency may be due to lack of IF secretion by gastric mucosa (eg, gastrectomy, gastric atrophy) or intestinal malabsorption (eg, ileal resection, small intestinal diseases).
Vitamin B12 deficiency frequently causes macrocytic anemia, glossitis, peripheral neuropathy, weakness, hyperreflexia, ataxia, loss of proprioception, poor coordination, and affective behavioral changes. These manifestations may occur in any combination; many patients have the neurologic defects without macrocytic anemia.
Pernicious anemia is a macrocytic anemia caused by vitamin B12 deficiency that is due to a lack of IF secretion by gastric mucosa.
Serum methylmalonic acid and homocysteine levels are also elevated in vitamin B12 deficiency states.
Reference Values
180-914 ng/L
Cautions
Patients taking vitamin B12 supplementation may have misleading results.
Recent vitamin B12 administration could result in normal or elevated serum concentrations.
Many other conditions are known to cause an increase or decrease in the serum vitamin B12 concentration including:
|
Increased Serum B12 |
Decreased Serum B12 |
|
Ingestion of vitamin C |
Pregnancy |
|
Ingestion of estrogens |
Aspirin |
|
Ingestion of vitamin A |
Anticonvulsants |
|
Hepatocellular injury |
Colchicine |
|
Myeloproliferative disorder |
Ethanol ingestion |
|
Uremia |
Contraceptive hormones |
|
|
Smoking |
|
|
Hemodialysis |
|
|
Multiple myeloma |
The evaluation of macrocytic anemia requires measurement of both vitamin B12 and folate levels; ideally they should be measured simultaneously.
Some patients exposed to animal antigens, either in the environment or as part of treatment or imaging procedure, may have circulating antianimal antibodies present. These antibodies may interfere with the assay reagents to produce unreliable results.
Day(s) Performed
Monday through Friday; 5 a.m.-12 a.m.
Saturday; 6 a.m.-6 p.m.
Report Available
Same day/1 dayPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.CPT Code Information
82607