A high level of vitamin B-12 can be an indicator of certain types of leukemia or liver disease. More often than not, high levels of the vitamin are flushed out of the body, WebMD says.
Patients are more likely to suffer from vitamin B-12 deficiency than the reverse, MedlinePlus claims. Excess vitamin B-12 is often removed in the urine and does not pose a problem for patients. Doctors do not generally use a vitamin B-12 blood test to find high levels of the substance. People who do have consistently high levels of the vitamin may have a serious condition. In rare cases, diabetics and obese people may have high levels of the vitamin, WebMD says.