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Lab Manual for Moffitt-Long and Mount Zion

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Vitamin B12

Item Value
Test Update Information
Approval req'd? No
Available Stat? No
Test code VB12
Performed by China Basin Chemistry
In House Availability Wednesday, Sunday (day shift)
Method Competitive immunoassay using direct chemiluminescent technology (Siemens Centaur)
Collection Instructions Avoid hemolysis.
Container type Gold top or Red top
Amount to Collect 1 mL blood
Sample type Serum
Preferred volume 0.5 mL serum
Min. Volume 0.25 mL serum
UCSF Rejection Criteria Hemolyzed
Processing notes Freeze serum at -20C within 24 hours of draw.
Units ng/L
Normal range
Normal 211-911 ng/L


Reference range adopted from vendor performed studies and verified by running blood donor samples (excluding autologous donors) collected at the UCSF Blood Donor Center.
Synonyms Cobalamin
Stability Room temperature 8 hours, refrigerated 2 days.
Turn around times 1-5 days
Additional information To convert ng/L to pmol/L (SI units) multiply by 0.738.

Cobalamin in the plasma and cytosol is bound to several proteins, including intrinsic factor, transcobalamins I and II and haptocorrin. Biologically active cobalamin is carried by intrinsic factor in the gut and by transcobalamin II in plasma. Changes in the other binding proteins ("R proteins"), can alter total cobalamin without affecting normal biological activity. Similarly, some patients may be deficient in biologically active forms of cobalamin despite "normal" or borderline low total cobalamin. If the measured cobalamin level is inconsistent with the clinical presentation, additional testing for increased serum levels of methylmalonic acid may be helpful in confirming or rejecting a diagnosis of B12-deficiency in individuals with normal or borderline low levels of cobalamin.
CPT coding 82607
LOINC code 2132-9
Last Updated 7/8/2013 11:00:30 AM
Entry Number 1000
Lab Procedure Link Click here for Procedure

If you have additional questions regarding this test, please call: 415-353-1667

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