High levels of vitamin B12 in the body are relatively unusual, but can occur as a result of liver disease, leukemia and bone marrow disorders such as polycythemia vera according to MedlinePlus. Occasionally, high vitamin B12 can be caused by diabetes, notes WebMD.
High levels of vitamin B12 in the body are relatively rare, as surplus amounts of the vitamin are typically expelled via urination, reports MedlinePlus. A simple blood test is used to determine vitamin B12 levels in the body, although it is typically administered to patients showing symptoms of vitamin B12 deficiency. However, the test can sometimes show higher than normal levels of vitamin B12, with the normal range differing from lab to lab. This is often indicative of an underlying medical condition such as liver disease or bone marrow disease or certain forms of leukemia, according to WebMD. Obesity can also lead to elevated vitamin B12 levels in the body, though this is rare.
While high levels of vitamin B12 are the result of serious medical disorders including cancer and liver disease, they are not considered to be definitive markers for these conditions, notes WebMD. As such, the vitamin B12 test is not administered to diagnose these disorders.