- **Normal range**: 200-900 picograms per milliliter (pg/mL…

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- **Normal range**: 200-900 picograms per milliliter (pg/mL) or 148-664 picomoles per liter (pmol/L).
- **Low levels**: Below 200 pg/mL (148 pmol/L) can indicate a deficiency.
- **High levels**: Levels above 900 pg/mL (664 pmol/L) might be considered high, but there is no universally agreed-upon upper limit for blood levels of B12.