Lab marker · Low

Low Vitamin B12 (Cobalamin): what it means

A Vitamin B12 (Cobalamin) result below the normal range is considered low. Here is what a reduced Vitamin B12 (Cobalamin) can point to, and when it is worth discussing with a doctor.

Reference range: 200–900 pg/mL; deficiency often suspected below 300

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What a low Vitamin B12 (Cobalamin) can 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.

How to raise a low Vitamin B12 (Cobalamin)

  • Eat more B12-rich foods - meat, fish, eggs and dairy; B12 comes almost only from animal sources.
  • If you are vegan or vegetarian, a B12 supplement or fortified foods are important - plant diets are a common cause of low B12.
  • Look for an absorption problem - metformin, long-term acid-reducing drugs, gastric surgery and pernicious anaemia block B12 uptake, and then diet alone is not enough.
  • Injections or high-dose oral B12 may be needed when absorption is the issue - your doctor will decide the route.
  • Recheck after your doctor advises - and check folate alongside.

General information, not a treatment plan - decisions about medication or target values belong with your doctor.

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Mediora.AI is informational - interpretation, not a diagnosis. A single out-of-range value is common and often benign; always discuss decisions with your doctor.