Section 14. Blood Disorders

Chapter 172. Anemia

Topics: Introduction | Anemia From Excessive Bleeding | Iron Deficiency Anemia | Vitamin Deficiency Anemia | Anemia of Chronic Disease | Autoimmune Hemolytic Anemia | Sickle Cell Disease | Hemoglobin C, S-C, and E Diseases | Thalassemias

Vitamin Deficiency Anemia

Vitamin deficiency anemia results from low or depleted levels of vitamin B₁₂ or folic acid (folate).

Vitamin B₁₂ deficiency and 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 Section 12, Chapter 154) or folic acid (see Section 12, Chapter 154) 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.

Symptoms and Diagnosis

Symptoms of anemia due to vitamin B₁₂ or folic acid deficiency develop slowly and are similar to symptoms produced by other types of anemia. Vitamin B₁₂ deficiency can also cause nerves to malfunction (see Section 12, Chapter 154).

Once anemia has been diagnosed, tests are performed to determine if a deficiency of vitamin B₁₂ or folic acid is the cause. Anemia due to vitamin B₁₂ or folic acid deficiency is suspected when large abnormal cells (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 a person has had megaloblastic anemia for a long time.

The blood levels of vitamin B₁₂ and folic acid are measured, and other tests may be performed to determine the cause of the vitamin deficiency.

Treatment

The treatment of anemia due to vitamin B₁₂ or folic acid 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. People who have anemia due to vitamin B₁₂ deficiency usually must take vitamin B₁₂ supplements for life.

Folic acid can be taken as one tablet daily. People who have trouble absorbing folic acid take supplements for life.