Vitamin B12 (Cyanocobalamine), Serum/Plasma


Vitamin B12 is a cofactor and coenzyme in many biochemical reactions such as the formation of succinyl coenzyme-A (CoA) from methylmalonyl CoA, a reaction essential to myelin formation and maintenance and the synthesis of methionine from homocysteine, which is required for DNA synthesis. The source of vitamin B12 is entirely dietary, mainly from foods of animal sources. In humans, vitamin B12 is complexed with the stomach-secreted intrinsic factor (IF) and is absorbed in the ileum. Possible causes of Vitamin B12 deficiency include dietary deficiency, lack of IF due to idiopathic atrophy of gastric mucosa, autoantibodies to parietal cells and IF, bacterial and parasitic intestinal colonisation, resection, or disease of the ileum and malabsorption.


Vitamin B12 deficiency can lead to pernicious anaemia in which decreased white blood cells & platelet counts and a hyper-cellular bone marrow with abnormal maturation are encountered. Vitamin B12 deficiency also causes many neuropsychiatric abnormalities due to demyelinisation of peripheral nerves, the spinal cord, cranial nerves and the brain that include decreased sensation, difficulty in walking, loss of control of bowel and bladder, optic atrophy, memory loss, dementia, depression and psychosis.

Sample Type, Quantity & Conditions

1 ml Serum 1 ml K2, K3-EDTA or Na, Li-Heparin Plasma Stability: 2 Hours at 15-25 °C 48 Hours at 2-8 °C 56 Days at (-15)-(-25) °C

Special Precautions

Freeze only once.

Normal Range

Normal: 197-770 pg/mL 145-569 pmol/L

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