Vitamin B12 (Cyanocobalamin / Methylcobalamin)

What Is Vitamin B12 (Cyanocobalamin / Methylcobalamin)?

Vitamin B12 (cobalamin) is an essential water-soluble vitamin and a cofactor for two human enzymes: methionine synthase, which converts homocysteine to methionine and is central to one-carbon metabolism and DNA methylation, and methylmalonyl-CoA mutase, which handles odd-chain fatty acid and branched-chain amino acid metabolism in mitochondria. Deficiency produces megaloblastic anaemia, peripheral neuropathy, fatigue, cognitive slowing, and in severe cases subacute combined degeneration of the spinal cord.

Oral B12 absorption requires intrinsic factor from gastric parietal cells and a functional terminal ileum, both of which can fail with age (atrophic gastritis), long-term metformin or proton-pump inhibitor use, bariatric surgery, autoimmune pernicious anaemia, or strict plant-based diets, since B12 is essentially absent from plant foods. Injectable B12 bypasses the absorption pathway entirely. Methylcobalamin, unlike cyanocobalamin, is the bioactive methylated form ready for direct enzymatic use, which is the rationale for its use in injectable formulations despite higher cost.