What role does B12 play in blood sugar?

Vitamin B12 (cobalamin) plays an indirect but physiologically relevant role in blood sugar metabolism. As a cofactor for methionine synthase, it is involved in the remethylation of homocysteine to methionine – a process important for DNA methylation and gene expression regulation. B12 deficiency can lead to elevated homocysteine levels, which are associated with oxidative stress and endothelial dysfunction – both factors that can impair insulin sensitivity. Additionally, B12 is essential for nerve function; deficiency can worsen or mimic diabetic neuropathy. Some observational studies suggest a link between low B12 levels and higher fasting glucose or insulin resistance, especially in metformin users (metformin lowers B12). However, the evidence is not strong enough for causal claims; randomized controlled trials are largely lacking. Clinical relevance is therefore limited: B12 supplementation does not directly improve glycemic control, but can support overall metabolic health if deficiency is confirmed. MyBody-X tests measure B12 in blood, but such results are not a medical diagnosis. Abnormal values should be discussed with a physician.