From the Research
Hypervitaminosis B12, or elevated vitamin B12 levels, is not typically harmful in itself but often serves as an important clinical marker for underlying conditions, and its effects are primarily related to its underlying causes rather than the elevated B12 itself. The effects of hypercobalaminemia are related to its underlying causes, which can include liver disease, certain blood disorders, kidney disease, and certain types of cancer 1. Some medications can also cause elevated B12 levels, including oral contraceptives and metformin.
Common Causes of Hypercobalaminemia
- Liver disease (particularly hepatitis and cirrhosis)
- Certain blood disorders (such as myeloproliferative disorders, polycythemia vera, and chronic myelogenous leukemia)
- Kidney disease
- Certain types of cancer
- Medications (including oral contraceptives and metformin)
Management Approach
Unlike vitamin toxicities from fat-soluble vitamins, excess B12 is generally considered safe as the body can eliminate unused water-soluble vitamins through urine. However, finding unexplained high B12 levels should prompt further investigation to identify the underlying cause, as treating the primary condition is the appropriate management approach rather than attempting to lower B12 levels directly. Laboratory testing to evaluate liver function, kidney function, and complete blood counts may be necessary to determine the cause of hypercobalaminemia 2, 3, 4, 5.
Key Considerations
- Elevated B12 levels are not a significant predictor of mortality after ICU admission when liver function is controlled for, and may instead be a proxy for poor liver function 2.
- Vitamin B12 supplementation might decrease serum levels of homocysteine in patients with non-alcoholic fatty liver disease, but further studies are needed to confirm this finding 3.
- Plasma levels of vitamin B12 in patients with decompensated chronic liver disease are high, whereas plasma folate levels are low, and the ratio between vitamin B12 and folic acid may be useful in the differential diagnosis of the etiology of chronic liver disease 4.