Elevated levels of B12 are rare and often caused by disease, most commonly decreased liver function or diseases of the blood. According to the Mayo Clinic, "Vitamin B12, or cobalamin, helps nerve cells, red blood cells and is used in the creation of DNA." Over-production of Vitamin B12 can be caused by cirrhosis, hepatitis, polycythemia vera or myelocytic leukemia. Vitamin B12 supplements will not cause elevated B12 blood levels.
Elevated levels of B12 can be caused by cirrhosis, scarring of the liver. Decreased liver function corresponds to elevated B12 levels because the liver cannot maintain B12 properly and the remainder is dispersed throughout the body. A 2003 study published in "Clinical Biochemistry" by Amphia Hospital in lokatie Langendijk, Breda, Netherlands, found the correlation between high B12 levels and people with cirrhosis. According to the Amphia Hospital study, "elevated levels are caused by cobalamin release during hepatic cytolysis and/or decreased cobalamin clearance by the affected liver."
Hepatitis, a disease that damages the liver, can cause an increase in cobalamin, which, according to the National Institutes of Health, is usually stored in the liver for years. If left untreated, hepatitis has the potential to go away, or it can cause liver failure or cancer. It also has the potential to turn into cirrhosis.
Chronic Myelocytic Leukemia
Chronic myelocytic leukemia or CML is cancer of the bone marrow that has been associated with elevated B12 levels. According to the "American Journal of Clinical Nutrition," the excess of B12 in those with CML could be caused by "serum proteins binding B12 more than liver proteins, or lack of B12 transferase as well as increased binding by serum proteins." This could be the cause of B12 to be improperly absorbed in the body.
Polycythemia vera is a disease characterized by over-production of red blood cells. The 2003 study published in "Clinical Biochemistry" by Amphia Hospital in lokatie Langendijk, Breda, Netherlands, found elevated B12 levels in polycythemia vera patients. Those with polycythemia vera cannot bind vitamin B12 properly, causing an over saturation of cobalamin. A B12 blood test to find elevated B12 levels can tell if someone has polycythemia vera. Polycthemia vera can result in myelofibrosis, a disease that is characterized by a decrease in white blood cells, red blood cells and platelets. Testing for elevated B12 levels in those with Myelofibrosis will also return positive.