High folic acid levels sometimes occur in people who have pernicious anemia, a rare disorder that causes a deficiency of vitamin B-12, according to WebMD. The human body needs vitamin B-12 to utilize folic acid, so when vitamin-B-12 levels are low, folic acid levels often rise.
Pernicious anemia is a disease that prevents the body from absorbing vitamin B-12, states WebMD. People with the disease lack intrinsic factor, a protein normally found in the intestines, and cannot absorb vitamin B-12 from food. Since vitamin B-12 is essential for the maturation of red blood cells, these people develop a form of anemia, with symptoms of pallor, tiredness, weakness and fatigue. Treatment consists of vitamin-B-12 injections or pills, the National Heart, Lung and Blood Institute explains.
Other factors and illnesses also cause vitamin-B-12 deficiency. These include chronic alcoholism, Crohn's disease, short-bowel syndrome and a vegan diet, explains Medical News Today.