Vitamin B12 (Cobalamin)
Also called: Vitamin B12, Cobalamin, B12
Vitamin B12 is essential for DNA synthesis, red blood cell formation and nerve function. Deficiency causes macrocytic anaemia and neurological symptoms.
Published: Updated:
Check your result
Calculated in your browser - the number is not sent anywhere.
Have the whole report? Upload it - we'll explain every value on it
What does Vitamin B12 (Cobalamin) measure?
Vitamin B12 comes from animal foods (meat, fish, dairy, eggs) and is absorbed in the terminal ileum with help from intrinsic factor secreted by the stomach. Liver stores hold years of B12, so deficiency develops slowly and can present without obvious dietary cause. Serum B12 is the standard screening test, but it can be normal in early deficiency — methylmalonic acid (more specific) and homocysteine (less specific) help confirm borderline cases.
What does a high Vitamin B12 (Cobalamin) level mean?
- Recent supplementation or B12 injections — almost always the cause.
- Liver disease — released B12 stores.
- Myeloproliferative neoplasms, certain leukaemias — rarely.
- High values are usually not actionable; the value matters when low.
What does a low Vitamin B12 (Cobalamin) level mean?
- Vegan / strict vegetarian diet — without supplementation, depletion is essentially inevitable.
- Pernicious anaemia — autoimmune destruction of gastric parietal cells, classic cause in older adults.
- Metformin — long-term use lowers B12 by 5–10% on average; check yearly in treated diabetics.
- Gastric surgery, ileal disease (Crohn's), proton pump inhibitors, atrophic gastritis.
- Older age — declining absorption is common.
When to discuss with a doctor
Symptoms of B12 deficiency (fatigue, paraesthesias, balance problems, glossitis) with a borderline-low value warrant follow-up with methylmalonic acid and a clinician visit. Neurological symptoms can be irreversible if deficiency is left untreated — see a doctor promptly. Mediora.AI flags borderline B12 alongside MCV (macrocytosis) in your report.
Related markers
Commonly confused with
- Methylmalonic acid (MMA) MMA is the confirming test, not an alternative one. B12 in the blood can look normal while the cells are already short of it; MMA rises in exactly that case, which is why it is ordered when the B12 result is borderline.