Nutrients
Vitamin B12 (cobalamin)
Cobalamin
Included in Baseline and Complete.
Compare membershipsYour nerves and red blood cells depend on B12.
Vitamin B12 helps make healthy red blood cells and keeps your nerves working properly. Your body stores a large supply, so low levels often develop slowly, over years.
Eating enough B12 doesn't always mean absorbing enough.
Natural sources of B12 are animal foods, and some plant-based products are fortified. Absorbing it depends on stomach acid and a protein called intrinsic factor. People on vegan diets, older adults, and people with pernicious anemia, celiac or Crohn's disease, or past stomach surgery are more likely to run low.
Long-term use of metformin or acid-reducing medicines can also lower B12. A borderline result is often followed up with methylmalonic acid (MMA), a related marker that rises when B12 runs low.
B12 stores change slowly, so trends over time matter.
Questions
Can my B12 look normal if I'm actually low?
It can. Serum B12 doesn't always reflect what your cells have available, so a result near the lower end of the range may be followed up with methylmalonic acid or homocysteine. Recent B12 supplements can also raise your blood level.
How do I make sense of a low result?
Low B12 is read alongside your blood counts, diet, medications, and symptoms. In the MyHealthspan app, an AI health assistant can explain it next to your other results, and a clinician can help find the cause, which matters as much as the number.