This test is often performed when other blood tests suggest a condition called megaloblastic anemia. Megaloblastic anemia is a blood disorder in which there is anemia with larger-than-normal red blood cells. A form of megaloblastic anemia is pernicious anemia which is caused when the person has poor vitamin B12 absorption. Low levels of B12 can cause numbness or tingling in the arms and legs, weakness, and loss of balance. Folate (Folic Acid) is a B vitamin that helps the body make healthy new cells.