What are the effects of hypercobalaminemia (elevated Vitamin B12 levels)?

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Last updated: April 24, 2025 • View editorial policy

From the Research

High vitamin B12 levels, or hypervitaminosis B12, typically don't cause significant health problems since excess B12 is usually excreted in urine. However, elevated B12 levels can sometimes indicate underlying medical conditions rather than being harmful themselves. These conditions may include liver disease, certain blood disorders like myeloproliferative disorders or leukemia, kidney disease, or certain types of cancer, as discussed in 1. Some medications can also raise B12 levels, including oral contraceptives and metformin. Symptoms rarely occur from high B12 itself, but when present might include acne, rosacea, or skin rashes. If you have unexpectedly high B12 levels, your doctor will likely investigate potential underlying causes rather than treating the B12 elevation directly, as suggested in 2, 3, 4, 1, 5. Unlike other vitamins, B12 toxicity from supplements is extremely rare because the body efficiently eliminates excess amounts. Key points to consider include:

  • Elevated B12 levels may indicate underlying medical conditions
  • Symptoms from high B12 are rare, but can include skin issues
  • Investigation of underlying causes is typically the course of action
  • B12 toxicity is rare due to the body's efficient elimination of excess amounts, as noted in 1. It's essential to follow up with your healthcare provider to determine if further testing is needed to identify any underlying conditions, as emphasized in 2, 3, 4, 1, 5.

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