Not Enough B12?

My sister, age 55, has just been diagnosed with pernicious anemia. Can it be reversed? Besides the shots she needs every two weeks, what dietary changes or supplements would help?

– February 4, 2014

Originally published January 20, 2004. Updated February 4, 2014.

Pernicious anemia is due to a vitamin B12 deficiency that leads to a low level of red blood cells. Because nerve cells also need B12, neurological symptoms such as dizziness, numbness and tingling in the hands and feet, and muscle weakness may show up even before the anemia is diagnosed.

It is possible that your sister’s condition is related to lack of B12 in her diet. Although we get this vitamin from animal foods (such as meat, fish, eggs or dairy products), which are plentiful in the average American diet, deficiencies in serum B12 still occur in about one in 30 adults over age 60. Dietary deficiencies are much more likely to develop among strict vegetarians (vegans) who eat no animal products; vegan children are especially susceptible.

In people your sister’s age or older, pernicious anemia is likely due to low "intrinsic factor," a protein produced in the stomach that is necessary for B12 absorption. Failure to produce intrinsic factor can be genetic in origin (about 20 percent of the relatives of pernicious anemia patients also have the disease, suggesting a genetic predisposition). Other causes of B12 deficiency include gastric surgery, abnormal bacterial growth in the small intestine, certain infections (especially tapeworms from fish) or intestinal disorders such as Crohn’s and celiac disease. While low B12 levels are more prevalent, pernicious anemia develops in only about two percent of the over-60 population; slightly more women than men are affected. Risks are highest among people who have autoimmune endocrine diseases.

Symptoms of vitamin B12 deficiency tend to come on so slowly that they may not be recognized for some time. They include fatigue, weakness, shortness of breath, dizziness, heart palpitations, bleeding gums and mouth sores, a red, beefy-looking tongue, nausea or poor appetite and diarrhea.

Before vitamin B12 treatments became available, pernicious anemia was often fatal. Today, while pernicious anemia resulting from low intrinsic factor cannot be reversed, B12 shots to correct the vitamin deficiency usually eliminate symptoms and restore the body’s production of red blood cells. At first, patients may get several shots to correct the deficiency and after that, regular injections every one to three months to maintain adequate B12 levels. In less severe cases, patients may be able to take enough B12 in the form of nasal gels or oral sprays.

In addition to your sister’s regular B12 shots, I recommend that she make sure that she’s getting adequate folic acid, at least 400 mcg a day, which is also needed for production of red blood cells. Apart from that, no special diet or supplements are necessary for anemia caused by low intrinsic factor.

Andrew Weil, M.D.

"What is Pernicious Anemia," National Heart, Lung and Blood Institute, accessed November 21, 2013,

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