From the Research
Vitamin B12 levels over 2,000 pg/mL are generally considered high and may be associated with an increased risk of cancer, but the evidence is not strong enough to establish a direct causal link, and the body has efficient mechanisms for regulating B12, making true toxicity extremely rare even with high supplementation. The normal range for vitamin B12 is typically between 200-900 pg/mL, and levels above 2,000 pg/mL are usually due to supplementation rather than natural causes 1. High B12 levels can sometimes mask underlying conditions like liver disease, certain blood disorders, or some cancers, so it is essential to investigate the cause, especially if supplements are not being taken 2. Some studies suggest that elevated B12 levels may be associated with a higher risk of cancer, with risk ratios ranging from 1.88 to 5.9, but the evidence is not consistent, and more research is needed to confirm this association 3. In patients with myeloproliferative neoplasms (MPNs), elevated B12 levels may serve as a diagnostic and prognostic biomarker, but the sensitivity, specificity, and cutoff levels are unclear 1. If symptoms such as acne, rosacea, or headaches are experienced, a doctor may recommend temporarily stopping supplements and retesting levels after a few weeks 4. Key points to consider include:
- High B12 levels are usually due to supplementation rather than natural causes
- Elevated B12 levels may be associated with an increased risk of cancer, but the evidence is not strong enough to establish a direct causal link
- The body has efficient mechanisms for regulating B12, making true toxicity extremely rare even with high supplementation
- It is essential to investigate the cause of high B12 levels, especially if supplements are not being taken
- Elevated B12 levels may serve as a diagnostic and prognostic biomarker in patients with MPNs, but more research is needed to confirm this association.