What is being tested?These tests measure the concentration of folate and vitamin B12 in the serum (liquid portion of the blood). The amount of folate inside the red blood cell (RBC) may also be measured -- it will normally be at a higher concentration inside the cell than in the serum.
B12 and folate are both part of the B complex of vitamins and come from food. Folate is found in leafy green vegetables, citrus fruits, dry beans and peas, liver, and yeast; while B12 is found in animal products such as red meat, fish, poultry, milk, and eggs. Fortified cereals, breads, and other grain products are now also important dietary sources of both B12 and folate (identified as “folic acid” on nutritional labels), especially for those vegetarians who do not consume any animal products.
Both B12 and folate are necessary for normal RBC formation, tissue and cellular repair, and DNA synthesis. B12 is also important for nerve health, while folate is necessary for cell division such as is seen in a fetus during pregnancy. A deficiency in either B12 or folate can lead to a form of anemia characterized by the production of fewer, but larger, RBCs (called macrocytes). A deficiency in B12 can also result in varying degrees of neuropathy, nerve damage that can cause tingling and numbness in the patient’s hands and feet. A deficiency in folate can cause
neural tube defects such as
spina bifida in a growing fetus.
