Vitamin B12 (Cobalamin)
Vitamin B12 is crucial for neurological function, DNA synthesis, and red blood cell production. Deficiency causes fatigue, cognitive decline, neuropathy, and megaloblastic anemia.
Vegans, the elderly, and those on metformin or PPIs are at higher risk of deficiency. Standard blood tests may miss functional deficiency — methylmalonic acid (MMA) is a better marker.
What It Measures
Serum B12 concentration.
Reference Ranges
| Status | Range (pg/mL) |
|---|---|
| Optimal | 500–1000 pg/mL |
| Normal | 200–900 pg/mL |
| Borderline | 200–400 pg/mL |
| Out of Range | < 200 pg/mL |
Optimal Ranges
| Group | Range | Unit | Source |
|---|---|---|---|
| Standard | 200–900 | pg/mL | Standard reference |
| Optimal (functional) | 500–800 | pg/mL | Functional range |
When Values Are High
Very high B12 (>1000 pg/mL) without supplementation may indicate liver disease, myeloproliferative disorders, or kidney dysfunction. Supplementation commonly causes elevated levels, which is generally benign.
When Values Are Low
B12 deficiency causes megaloblastic anemia, neurological damage (peripheral neuropathy, cognitive decline), fatigue, and depression. Deficiency is common in vegans, elderly, and those on metformin or PPIs.
What To Do
Lifestyle
- •Include animal products (meat, fish, eggs, dairy) for dietary B12
- •Vegans/vegetarians must supplement — no reliable plant sources exist
- •Older adults may need supplements due to reduced absorption
Supplements
- •Methylcobalamin 1000mcg sublingual daily
- •B12 injections for severe deficiency or absorption issues
- •Check methylmalonic acid (MMA) for functional deficiency if B12 is borderline
When to Retest
Retest 8–12 weeks after starting supplementation; check MMA for accuracy
How GATOR Tracks This
Lab Providers
Related Biomarkers
This content is for informational purposes only and does not constitute medical advice. Reference ranges may vary by laboratory and individual factors. Consult a qualified healthcare provider for interpretation of your results and treatment decisions.
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