Vitamin B12

What is Vitamin B12?

Vitamin B12 (cobalamin) is an essential water-soluble vitamin required for DNA synthesis, red blood cell formation, myelin sheath maintenance (nerve insulation), and methylation reactions. It is exclusively found in animal products. Absorption requires intrinsic factor from stomach parietal cells and an intact ileum.

What might a high or low Vitamin B12 mean?

B12 deficiency causes megaloblastic anemia (large, immature RBCs with high MCV) and neurological damage (peripheral neuropathy, cognitive decline, depression) that can be irreversible if untreated. Deficiency is common in elderly (10-15% over age 60), vegans, those on metformin or PPIs, and people with autoimmune gastritis.

What is the typical reference range for Vitamin B12?

The general-population reference range shown here is 148 – 616 pmol/L. Reference ranges describe the general population and are not a personal target — discuss your results with your physician.

What can affect Vitamin B12?

It may be higher with: B12 supplementation (methylcobalamin or hydroxocobalamin), B12 injections (intramuscular — bypasses absorption issues), Animal products (meat, fish, eggs, dairy), Fortified foods (nutritional yeast, plant milks). It may be lower with: Vegan/vegetarian diet (no animal sources), Pernicious anemia (autoimmune intrinsic factor destruction), Atrophic gastritis (reduced acid and IF production), Metformin (impairs B12 absorption — up to 30% of users), Proton pump inhibitors (reduce stomach acid needed for B12 release), Crohn's disease or ileal resection, Aging (reduced absorption capacity), Nitrous oxide exposure (inactivates B12).