Vitamin B12 and folate are two vitamins that are part of the B complex of vitamins. They are necessary for normal red blood cell (RBC) formation, repair of tissues and cells, and synthesis of DNA, the genetic material in cells. Both are nutrients that cannot be produced in the body and must be supplied by the diet.
Vitamin B12 and folate tests measure vitamin levels in the liquid portion of the blood (serum or plasma) to detect deficiencies. Sometimes the amount of folate inside red blood cells may also be measured.
Folate refers to a natural occurring form of the vitamin, whereas folic acid refers to the supplement added to foods and drinks. It is found in leafy green vegetables, citrus fruits, dry beans and peas, liver, and yeast. Vitamin B12, also called cobalamin, is found in foods from animals, such as red meat, fish, poultry, milk, yogurt, and eggs. In recent years, fortified cereals, breads, and other grain products have also become important dietary sources of B12 and folate (identified as “folic acid” on nutritional labels).
A deficiency in either B12 or folate can lead to macrocytic anemia, where red blood cells are larger than normal. Megaloblastic anemia, a type of macrocytic anemia, is characterized by the production of fewer but larger RBCs called macrocytes, in addition to some cellular changes in the bone marrow. Other laboratory findings associated with megaloblastic anemia include decreased white blood cell (WBC) count and platelet count.
B12 is also important for nerve health and a deficiency can lead to varying degrees of neuropathy, nerve damage that can cause tingling and numbness in the affected person’s hands and feet.