Excess vitamin B12 in the blood can appear because of high dietary intake or supplementation. Excess B12 is harmless because the vitamin is excreted in urine, but high serum vitamin B12 can be indicative of a serious life-threatening disorder involving the liver or blood. It should be suspected when plasma concentration of B12 is greater than 660 pmol or 900 pg/mpmol.
Blood Disorders
Blood cancers, or leukemias, and another type of blood disorder called myeloproliferative disorder, which is a group of conditions that cause blood cells including platelets, white blood cells, and red blood cells to grow abnormally in the bone marrow, increase high serum vitamin B12 levels. The conditions by increase synthesis of vitamin B12 transport proteins and decrease their removal from the blood by the kidneys.
Hypereosinophilic Syndromes
Hypereosinophilic syndrome is a disease characterized by abnormal elevation of eosinophil cell count in the blood for at least six months without any recognizable cause. Eosinophils are cells that participate in allergic reaction and immune response. It is a serious condition and affects the heart, lungs and liver. High serum vitamin B12 concentrations may be caused by increased B12 transport proteins.
Liver Diseases
Liver diseases, including cancer, cirrhosis and hepatitis, may also cause elevated serum vitamin B12 concentrations. The reason behind this is increased B12 transport proteins and increased release of vitamin B12 from the liver.
References
- "Goodman & Gilman's The Pharmacological Basis of Therapeutics"; Laurence L. Brunton, John S. Lazo and Keith L. Parker; 2006
- "Clinical Biochemistry"; Significance of Elevated Cobalamin (Vitamin B12) Levels in Blood; Ermens AA, Vlasveld LT, Lindemans J.; November 2003
- "Clinical Chemistry"; gG--IgM--Vitamin B12 Immune Complexes; Raffick A.R. Bowen, Steven K. Drake, Rachna Vanjani, Edward D. Huey, Jordan Grafman and McDonald K. Horne; 2006
