Vitamin B12 is needed to produce an adequate amount of healthy red blood cells in the bone marrow. Vitamin B12 is available only in animal foods (meat and dairy products) or yeast extracts (such as brewer's yeast). Vitamin B12 deficiency is defined by low levels of stored B12 in the body that can result in anemia, a lower-than-normal number of red blood cells.
Vitamin B12 deficiency can develop for the following reasons:
In children, decreased levels of intrinsic factor can be an inherited (genetic) condition. When this happens, low levels of intrinsic factor produce symptoms of juvenile pernicious anemia in patients younger than age 10.
Pernicious anemia occurs more commonly in people who already have diseases that are linked to immune-system abnormalities, such as Graves' disease, hypothyroidism (under-functioning thyroid gland), thyroiditis (inflammation of the thyroid), vitiligo and Addison's disease (adrenocortical insufficiency).
Symptoms tend to develop slowly and may not be recognized immediately. As the condition worsens, common symptoms include:
If low levels of B12 remain for a long time, the condition also can lead to irreversible damage to nerve cells, which can cause the following symptoms:
Your doctor will ask you about your diet and about any family history of anemia. Your doctor also will review your medical history for medical illnesses (diabetes, immune disorders) or surgeries, such as stomach removal, that can lead to B12 deficiency.
Your doctor may suspect that you have vitamin B12 deficiency based on your medical history and symptoms. To confirm the diagnosis, he or she will examine you and order laboratory tests. During the physical examination, your doctor will look for a red, beefy tongue, pale or yellowish skin, a rapid pulse and heart murmurs resulting from an anemia-related increase in blood flow demands on the heart. Laboratory tests will include:
With proper treatment, symptoms of vitamin B12 deficiency begin to improve within a few days. In vegans and other people whose B12 deficiency is diet-related, oral B12 supplements and a diet designed to increase consumption of vitamin B12 should cure the condition. People with pernicious anemia or people who cannot absorb vitamin B12 from their intestines will need injections of vitamin B12 every one to three months indefinitely.
To prevent vitamin B12 deficiency, vegans should take adequate amounts of vitamin B12 supplements to make up for the shortage in their diet.
For people who cannot absorb B12, the condition cannot be prevented. However, once it is diagnosed, regular injections of vitamin B12 will prevent symptoms from returning.
Treatment for this condition involves replacing the missing vitamin B12. People who cannot absorb B12 need regular injections. When injections first are administered, a patient with severe symptoms may receive five to seven during the first week to restore the body's reserves of this nutrient. A response usually is seen within 48 to 72 hours, with brisk production of new red blood cells. Once B12 reserves reach normal levels, injections of vitamin B12 will be needed every one to three months to prevent symptoms from returning. People who cannot absorb vitamin B12 should continue to eat a well-balanced diet that provides other nutrients (folic acid, iron and vitamin C) necessary to produce healthy blood cells. Sometimes people can take high doses of oral B12 to provide replacement instead of undergoing injections, but a physician should closely supervise this.
In people whose vitamin B12 deficiency is related to overgrowth of intestinal bacteria, treatment with oral antibiotics, such as tetracycline (sold under several brand names) may stop bacterial overgrowth and allow the absorption of vitamin B12 to return to normal.
Vitamin B12 deficiency resulting from inadequate dietary intake is the easiest to treat. The condition can be reversed by taking oral vitamin B12 supplements and adding foods containing B12.
When the anemia is severe and the red blood cell count is extremely low, blood transfusions may be necessary for the first couple of days until the vitamin B12 injections begin working.
Contact your doctor for a physical examination if you experience unexplained fatigue, palpitations, shortness of breath, sore tongue or any other symptoms of vitamin B12 deficiency. This is especially true if you are a vegan, are older than age 50 and of African-American or Northern-European descent, have diabetes, have an autoimmune disorder or have had your stomach removed.
The outlook is excellent because this form of anemia responds well to treatment. However, it is possible that nerve cell damage will be permanent. Some residual damage to the nervous system may remain in people who sought treatment late in the illness.
National Heart, Lung, and Blood Institute (NHLBI)
P.O. Box 30105
Bethesda, MD 20824-0105