How to Convert Vitamin B12 pg/mL to pmol/L
Vitamin B12 (cobalamin) is reported in pg/mL in the US and pmol/L in most other countries. The values describe the same blood level, so converting lets you compare a result with reference ranges from either system. Note that pg/mL and ng/L are the same number (1 pg/mL = 1 ng/L).
The conversion factor between pg/mL and pmol/L is 0.738:
B12 pmol/L = B12 pg/mL × 0.738 B12 pg/mL = B12 pmol/L ÷ 0.738 Vitamin B12 pg/mL to pmol/L Chart
Reference ranges vary by laboratory, so compare with the range printed on your own report.
| pg/mL (= ng/L) | pmol/L | Typical status |
|---|---|---|
| 150 pg/mL | 110.7 pmol/L | Low — deficiency range |
| 200 pg/mL | 147.6 pmol/L | Lower limit of many ranges |
| 300 pg/mL | 221.4 pmol/L | Borderline / gray zone |
| 400 pg/mL | 295.2 pmol/L | Normal |
| 500 pg/mL | 369.0 pmol/L | Comfortably normal |
| 600 pg/mL | 442.8 pmol/L | Normal |
| 900 pg/mL | 664.2 pmol/L | Upper limit of many ranges |
pmol/L to pg/mL Reverse Chart
| pmol/L | pg/mL (= ng/L) |
|---|---|
| 148 pmol/L | 200.5 pg/mL |
| 200 pmol/L | 271.0 pg/mL |
| 300 pmol/L | 406.5 pg/mL |
| 400 pmol/L | 542.0 pg/mL |
| 500 pmol/L | 677.5 pg/mL |
| 664 pmol/L | 899.7 pg/mL |
Normal and Deficient Vitamin B12 Ranges
Commonly cited educational bands (they vary by laboratory and assay):
| Status | Conventional (pg/mL) | SI (pmol/L) |
|---|---|---|
| Deficient | Below 200 pg/mL | Below 148 pmol/L |
| Borderline / gray zone | 200–300 pg/mL | 148–221 pmol/L |
| Normal (often cited) | 200–900 pg/mL | 148–664 pmol/L |
Why a "Normal" B12 Can Still Be Deficient
Serum B12 measures total cobalamin, much of which is bound and not readily usable by cells. As a result, a value in the gray zone (200–300 pg/mL) — or sometimes even a "normal" result — can hide a functional deficiency. When B12 is borderline and symptoms suggest deficiency, clinicians check homocysteine and methylmalonic acid (MMA), which rise when active B12 is low.
B12 is part of the anemia work-up alongside folate and iron studies such as ferritin. Macrocytic anaemia in particular points toward B12 or folate deficiency.
Worked Example
Suppose your B12 is 250 pg/mL and you want pmol/L:
250 × 0.738 = 184.5 pmol/L 184.5 pmol/L sits in the borderline gray zone, where MMA or homocysteine may be checked. For the reverse direction, 148 pmol/L is about 200 pg/mL.
Frequently Asked Questions
How do you convert B12 pg/mL to pmol/L?
Multiply pg/mL by 0.738. For example, 400 pg/mL equals about 295 pmol/L.
Is pg/mL the same as ng/L for B12?
Yes. 1 pg/mL equals 1 ng/L exactly, so the number does not change.
What B12 level is deficient?
Below 200 pg/mL (about 148 pmol/L) suggests deficiency; 200–300 pg/mL is a borderline gray zone.
Why check MMA and homocysteine?
They confirm functional B12 status when serum B12 is borderline, because both rise when active B12 is low.
References
- Merck Manual Professional Edition — Vitamin B12 Deficiency (B12 reference values and interpretation).
- Cobalamin conversion factor 1 pg/mL = 0.738 pmol/L; pg/mL = ng/L (1:1) (standard clinical laboratory unit conversion).
Conclusion
Converting vitamin B12 between pg/mL and pmol/L is a simple multiply or divide by 0.738 (and pg/mL equals ng/L). Just remember that a borderline or even normal B12 can still be functionally low — interpret it with MMA, homocysteine, folate, and your healthcare provider.