Vitamin deficiency anemia results from low or depleted levels of vitamin B12 or folate (folic acid).
Vitamin B12 deficiency and folate (folic acid) deficiency cause megaloblastic anemia. In megaloblastic anemia, the bone marrow produces red cells that are large and abnormal (megaloblasts).
Deficiency of vitamin B12 (see Vitamins: Vitamin B12 Deficiency) or folate (see Vitamins: Folate Deficiency) most often develops due to a lack of these vitamins in the diet or an inability to absorb these vitamins from the digestive tract. Deficiency of these vitamins is sometimes caused by drugs used to treat cancer, such as methotrexate, hydroxyurea, fluorouracil, and cytarabine. A form of vitamin B12 deficiency called pernicious anemia results from an inability to absorb vitamin B12 from the diet.
Symptoms and Diagnosis
Symptoms of anemia due to vitamin B12 or folate deficiency develop slowly and are similar to symptoms caused by other types of anemia. Vitamin B12 deficiency can also cause nerves to malfunction, causing tingling, loss of sensation, and muscle weakness (see Vitamins: Vitamin B12 Deficiency).
Once anemia has been diagnosed, tests are done to determine if a deficiency of vitamin B12 or folate is the cause. Anemia due to vitamin B12 or folate deficiency is suspected when megaloblasts are seen in a blood sample that is examined under a microscope. Changes in white blood cells and platelets also can be detected, especially when people have had megaloblastic anemia for a long time.
The blood levels of vitamin B12 and folate are measured, and other tests may be done to determine the cause of the vitamin deficiency.
The treatment of anemia due to vitamin B12 or folate deficiency consists of replacing the deficient vitamin.
Commonly, vitamin B12 is administered by injection. At first, injections are given daily or weekly for several weeks until the blood levels of vitamin B12 return to normal. Then injections are given once a month. Vitamin B12 can also be taken daily as a nose spray, a tablet placed under the tongue, or a tablet that is swallowed. Generally, intramuscular injections of vitamin B12 are necessary to correct pernicious anemia. People who have anemia due to vitamin B12 deficiency usually must take vitamin B12 supplements for life.
Folate can be taken as one tablet daily. People who have trouble absorbing folate take supplements for life.
Last full review/revision June 2008 by Alan E. Lichtin, MD