Anemia is a drop in the number of red blood cells. This can be caused by a lack of vitamin B12.

Vitamin B12 is essential for normal nervous system function and blood cell production. The main sources of vitamin B12 include meat, eggs, and dairy products. For vitamin B12 to be absorbed by the body, it must bind to intrinsic factor, a protein secreted by cells in the stomach.

Causes of vitamin B12 deficiency include:

• A diet low in vitamin B12 (for example, a strict vegetarian diet that excludes all meat, fish, dairy products, and eggs)
• Chronic alcoholism
• Abdominal or intestinal surgery that affects intrinsic factor production or absorption
• Crohn's disease
• Intestinal malabsorption disorders
• Fish tape worm
• Pernicious anemia, which is caused by a lack of intrinsic factor

The risk factors are related to the causes.

• Loss of appetite
• Diarrhea
• Numbness and tingling of hands and feet
• Paleness
• Shortness of breath
• Fatigue
• Weakness
• Sore mouth and tongue
• Confusion or change in mental status in severe or advanced cases

A physical evaluation of the patient's neurological signs may show depressed deep tendon reflexes, decreased position sense, decreased vibration sense, or positive Babinski reflex. Other signs and tests include the following:

• CBC results show low hematocrit with an elevated MCV
• Bone marrow examination
• Elevated LDH
• Below-normal vitamin B12 level
• Schilling test (to determine where the deficiency in B12 absorption lies).

Treatment depends on the cause of the anemia:

• Pernicious anemia requires lifelong therapy with vitamin B12 injections.
• Anemia caused by a lack of vitamin B12 can be corrected by vitamin pills combined with a more balanced diet. It may be treated initially with vitamin B12 injections.
• Anemia caused by malabsorption is treated with vitamin B12 injections until the condition improves.

Treatment for this form of anemia is usually effective.

• The signs and symptoms related to the central nervous system may be irreversible if treatment is not begun within 6 months of when these symptoms begin.
• Vitamin B12 affects epithelial cells (cells that form the outer surface of the body and line inner passageways). Therefore, a lack of B12 may cause a false-positive Pap smear.

Call your health care provider if you have any of the symptoms of anemia.

Anemia caused by a lack of vitamin B12 can be prevented through a well-balanced diet. B12 injections can prevent anemia after surgeries known to cause vitamin B12 deficiency. Early diagnosis and prompt treatment can limit the severity of this anemia as well as the neurologic complications.