Facebook Pixel Code
Section banner image
Paediatric Laboratory Medicine

Vitamin B12, Blood

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.

Test Name

Vitamin B12, Blood

Test Code



Biochemistry - Biochemistry


Abbott Ci4100

External Proficiency Testing


Turn Around Time

Monday to Friday

Specimen Type

Serum, Lithium Heparin / Dipotassium EDTA plasma

Minimum Specimen Requirements

150 uL



Approval is not required

CPT Codes


Shipping and Contact Information

The Hospital for Sick Children
Rapid Response Laboratory
170 Elizabeth Street, Room 3642
Toronto, ON
M5G 2G3
Phone: 416-813-7200
Phone: 1-855-381-3212

Reference Range

5d - < 1y : 191-1164 pmol/L
1- <9y : 218-1305 pmol/L
9-<14y : 186-830 pmol/L
14-<17y : 180-655 pmol/L
17-<19y : 150-599 pmol/L