vitamin B12 test (cyanocobalamin), a blood test that measures levels of vitamin B12, which is necessary for conversion of the inactive form of folate to the active form, a process that is crucial in the formation and function of red blood cells. Abnormal levels may indicate leukemia, severe liver dysfunction, myeloproliferative disease, pernicious anemia, malabsorption syndromes, inflammatory bowel disease, and Zollinger-Ellison syndrome, among other conditions.
