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Vitamin B12, serum or plasma

Alternate test name


Lab area
Clinical Biochemistry - General
Method and equipment
Abbott Architect Ci-4100
Expected turn-around time
STAT/ Urgent: 6 Hours Routine: 24 Hours
Specimen type

Serum, Lithium Heparin / Dipotassium EDTA plasma

Specimen requirements

150 uL

Storage and transportation


Shipping information
The Hospital for Sick Children
Rapid Response Laboratory
555 University Avenue, Room 3642
Toronto, ON
M5G 1X8
Phone: 416-813-7200
Toll Free: 1-855-381-3212
Hours: 7 days/week, 24 hours/day
Background and clinical significance

Vitamin B12 (cobalamin) in serum is bound to two proteins: transcobalamin (TC) and haptocorrin (HC). The transcobalamin-vitamin B12 complex is called holotranscobalamin (HoloTC). HoloTC contains the biologically available cobalamin as only HoloTC promotes the uptake of cobalamin by all cells via specific receptors. Methods based on specific anti-TC antibodies have been available and confirm the usefulness of HoloTC for diagnosing B12 deficiency. As expected, HoloTC levels are low in patients with biochemical signs of vitamin B12 deficiency. Notably, low values have been reported in vegetarians, vegans, and in populations with a low intake of vitamin B12. In addition, low levels of HoloTC (but not vitamin B12) in serum were reported in patients with Alzheimer’s disease compared to levels of HoloTC in a healthy control group.

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