Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Crohn's Disease Can Be a Factor in B12 Deficiency

Dear Doctor: I'm living with Crohn's disease. Even though I feel fine, my wife is certain that it has caused me to be vitamin B12 deficient. If you could explain the signs of a B12 deficiency, it may put her mind at ease and get me off the hot seat.

Dear Reader: When you have Crohn's disease, a portion of your digestive tract is chronically irritated or inflamed. Symptoms include pain or cramping in your abdomen, diarrhea, fever and weight loss. The cause of Crohn's disease, one of a group of disorders known as inflammatory bowel disease (IBD), is not known at this time. However, changes in diet and the use of medications to reduce inflammation, along with bowel rest, can help relieve symptoms.

The reason your wife is concerned about your levels of vitamin B12 is that Crohn's disease can cause the tissue of the bowel to thicken, become scarred or develop ulcers. Any of these may cause the bowel to lose the ability to properly absorb nutrients. When the disease is located at the far end of the small intestine, where vitamin B12 absorption takes place, maintaining healthy levels of that vitamin can indeed become an issue.

We need about 2.4 micrograms of B12 per day for our bodies to carry out functions like making red blood cells, keeping our nerves healthy and making DNA. Sources of B12 include fish, meat, poultry, eggs, milk and other dairy products, with liver and clams delivering a particularly hefty dose of the vitamin. It's also added to some breakfast cereals and is available as a supplement.

Although most people in the United States get enough B12 through a balanced diet, up to 15 percent of Americans have some degree of deficiency. Some older adults lack adequate hydrochloric acid in their stomachs to properly separate B12 from food. That means that when the contents of the stomach reaches the end of the small intestine, B12 is not available in a form that can be absorbed. In individuals like yourself, whose bowel is chronically inflamed, absorption in the small intestine can become compromised, even with proper digestion in the stomach.

Symptoms that can indicate a vitamin B12 deficiency include feeling weak and tired for no apparent reason, mental confusion or "fogginess," a decline in balance, the onset of depression and even signs of dementia. Other indicators may be poor appetite, unexplained weight loss, ongoing constipation and nerve problems like prickling or tingling in the hands or feet. In extreme cases, a deficiency of vitamin B12 can lead to megaloblastic anemia, which can cause extreme fatigue, dizziness and pale skin.

If these symptoms sound familiar, your family doctor will measure your B12 levels via a simple blood or urine test. Should a deficiency be found, treatment may include a diet of foods rich in B12, regular B12 supplements or, in a severe case, B12 injections. And considering that long-term B12 deficiency can cause nerve damage and other serious problems, we would also prescribe a "thank you" to your wife.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)