Vitamin B12 deficiency
Common, often-missed deficiency that can cause macrocytic anaemia, fatigue and — if untreated — irreversible nerve damage. Easily diagnosed and treated once spotted.
What it is
Vitamin B12 (cobalamin) is required for red-cell production, DNA synthesis and the myelin sheath around nerves. Deficiency develops over months to years and falls into two big buckets: dietary (strict vegan / vegetarian without supplementation) and absorptive (pernicious anaemia, atrophic gastritis, post-bariatric surgery, terminal-ileum disease, long-term metformin or proton-pump inhibitor use). The classic blood picture is macrocytic anaemia (high MCV) with low B12, raised homocysteine and raised methylmalonic acid; nervous-system damage can precede haematological signs.
Key lab markers
- Vitamin B12 — values <200 pg/mL strongly suggest deficiency; 200–300 is borderline and often confirmed with MMA or homocysteine.
- Homocysteine — rises early in functional deficiency.
- MCV — macrocytic (high MCV) anaemia is the classic finding.
- Folate — must be checked together; folate supplementation can correct the anaemia while letting nerve damage progress.
Symptoms
- Fatigue, breathlessness on exertion (from anaemia)
- Glossitis, mouth ulcers
- Tingling, numbness or weakness in hands and feet
- Difficulty walking, balance problems
- Memory problems, cognitive slowing
- Depression
When to discuss with a doctor
Suspected deficiency warrants a primary-care visit. Treatment is straightforward — oral or intramuscular B12 — but identifying the cause matters: pernicious anaemia needs lifelong replacement; long-term PPI users may need ongoing supplementation. Mediora.AI flags low B12 alongside MCV and homocysteine for the early functional pattern.