Is a vitamin B12 (cobalamin) level of 752 picograms per milliliter (pg/mL) concerning?

Elevated Vitamin B12 Level of 752 pg/mL: Clinical Significance

A vitamin B12 level of 752 pg/mL is not concerning and suggests vitamin B12 deficiency is unlikely, as it is well above the threshold of 350 ng/L (258 pmol/L) that indicates sufficient B12 status according to current guidelines. 1

Interpreting Elevated B12 Levels

According to the 2024 NICE guidelines, vitamin B12 levels are interpreted as follows:

• Less than 180 ng/L (133 pmol/L): Confirmed vitamin B12 deficiency
• 180-350 ng/L (133-258 pmol/L): Indeterminate result - possible deficiency
• More than 350 ng/L (258 pmol/L): Vitamin B12 deficiency is unlikely 1

At 752 pg/mL (equivalent to 752 ng/L), your level is significantly above the threshold that would indicate deficiency or even an indeterminate result.

Potential Causes of Elevated B12 Levels

While not concerning from a deficiency perspective, it's worth noting that elevated B12 levels can sometimes be associated with:

1. Vitamin B12 supplementation - The most common cause of elevated levels 2
2. Laboratory artifacts - Including macro-vitamin B12, which can cause falsely elevated readings 3
3. Medical conditions - In some cases, elevated B12 has been associated with:
   • Liver disorders 4, 5
   • Certain malignancies 4, 5
   • Renal failure 4
   • Inflammatory or autoimmune diseases 4

Clinical Implications

For most individuals, an elevated B12 level of 752 pg/mL without symptoms is not a cause for concern:

• In otherwise healthy individuals: High B12 levels often have benign causes and may decrease slightly over time 6
• No treatment needed: No intervention is required for asymptomatic individuals with elevated B12 2

When Further Evaluation May Be Warranted

Consider additional evaluation only if:

• There are unexplained symptoms despite elevated B12 levels
• There are risk factors for conditions associated with elevated B12
• The elevation is extreme (typically >1000 pg/mL) 6

Important Considerations

1. Functional B12 status: In some cases, normal or high serum B12 may not accurately reflect functional B12 status. If there are symptoms suggestive of B12 deficiency despite normal/high levels, testing methylmalonic acid (MMA) may be warranted 2

2. Macro-vitamin B12: This is an underrecognized cause of falsely elevated B12 readings. If the elevated level cannot be explained by supplementation or medical conditions, macro-vitamin B12 should be considered 3

3. Monitoring: For significantly elevated levels (>1000 pg/mL), some clinicians recommend periodic follow-up, as a small percentage of children with unexplained high B12 developed leukemia in follow-up studies 6

In conclusion, a B12 level of 752 pg/mL is above normal reference ranges but is not concerning from a deficiency perspective and typically does not require intervention unless accompanied by unexplained symptoms or risk factors for conditions associated with elevated B12.