B12 Deficiency & Macrocytic Anemia

Vitamin B12, or cobalamin, is an essential nutrient obtained from the diet. Patients with a vitamin B12 deficiency commonly develop a shortage of red blood cells, or macrocytic anemia. Several diseases and medical conditions can lead to vitamin B12 deficiency and a related macrocytic anemia. Correction of the deficiency typically leads to restoration of a normal red blood cell level.

Impairment

The bone marrow produces red blood cells to replenish those removed from the circulation by the liver and spleen. The production of red blood cells requires vitamin B12, which aids in the formation of genetic material for the new cells. Insufficient cobalamin leads to slow, abnormal red blood cell production, notes the medical reference text "Hematology Clinical and Laboratory Practice." This depressed production rate leads to a red blood cell deficit and produces abnormally large, or macrocytic red blood cells. Thus, a vitamin B12 deficiency leads to macrocytic anemia, also known as megaloblastic or pernicious anemia.

Causes

Patients become vitamin B12 deficient primarily because of impaired absorption of the nutrient or an inadequate dietary supply. Intestinal absorption of vitamin B12 requires the chemical intrinsic factor, produced by the stomach. An inherited inability to produce intrinsic factor, or loss of intrinsic factor-producing cells in the stomach, can cause impaired intestinal absorption of vitamin B12, leading to a deficiency, explains the National Heart Lung and Blood Institute. Gastric bypass surgery or removal of all or part of the stomach can also cause an intrinsic factor deficit and vitamin B12 deficiency.

Patients with poor quality diets may develop a vitamin B12 deficiency. Strict vegans may also become vitamin B12 deficient because the nutrient does not occur in plants, notes "Hematology Clinical and Laboratory Practice."

Symptoms

Many symptoms of vitamin B12 deficiency-related macrocytic anemia prove indistinguishable from other types of anemia symptoms such as paleness, fatigue, shortness of breath and reduced exercise tolerance.

Symptoms that point to the possibility of an underlying vitamin B12 deficiency include tingling of the hands and feet, muscle weakness, diarrhea or constipation, nausea, weight loss, decreased appetite, loss of balance or coordination, and a red, irritated tongue, notes the National Heart Lung and Blood Institute.

Treatment

Vitamin B12 injections prove the mainstay of treatment for patients with macrocytic anemia caused by impaired absorption of the nutrient, notes New York-Presbyterian Hospital. For patients with a dietary deficiency, doctors may recommend oral vitamin B12 supplements. Patients typically have blood tests in the weeks following the initiation of treatment to monitor for correction of the anemia.

Prevention

Patients without an underlying impairment of vitamin B12 absorption can prevent a deficiency by consuming a healthful diet that includes foods rich in the nutrient. Foods with a high concentration of vitamin B12 include eggs, milk products, fish, poultry, beef and liver. Although plants do not contain vitamin B12, food manufacturers commonly add the nutrient to cereals and other grain products, reports the National Institutes of Health Office of Dietary Supplements.