When should you be tested for vitamin B12?

Two recent patient experiences prompted this post. In the Wall Street Journal, Dana Hawkins-Simons described several years of being seen by specialist after specialist for her complaints of tiredness, dizziness, ringing in the ears, palpitations, shortness of breath and “brain fog.” She finally researched her symptoms and demanded that she be checked for vitamin B12 deficiency, which turned out to be the cause of her symptoms.

Recently, the British Medical Journal published the case of a 69-year-old woman who was diagnosed with multiple sclerosis based on her rapidly worsening symptoms of hand and leg weakness and numbness, slurred speech, poor concentration, and urinary symptoms. At the center where she went for a second opinion, B12 deficiency was suspected and proved to be the cause of her symptoms rather than MS. Fortunately, she had not yet begun on the previously recommended immune-suppressive MS treatment.

Vitamin B12 is critical to many body functions. It is needed to build blood cells, and B12 deficiency was the cause of pernicious anemia, so-called because 100 percent of sufferers died. Dr. George Minot’s discovery of the effectiveness of liver therapy in 1926 saved these people, even though no one was sure why it worked. Another pioneer working at the Boston City Hospital, Dr. Bill Castle, identified Vitamin B12 and allowed B12 injections to take the place of crude liver extracts. The neurologic system also needs B12, and deficiency can lead to many neuropsychiatric symptoms, including numbness of the extremities, an unsteady gait, forgetfulness or even dementia, irritability or depression, vision loss and a shock-like sensation down the spine with neck flexion (that is also seen in MS!). The tongue may be swollen, smooth, and tender.

How does one get deficient in B12? The classic cause, most frequent in older adults, particularly those of northern European ancestry, is pernicious anemia, in which the body is unable to absorb B12 due to lack of the protein needed to allow it to pass through the intestine into the body. It was thought that dietary lack was uncommon because B12 is found in so many foods, but these are all of animal origin, and it is easy for strict vegans to become deficient if they do not take supplements. There may be decreased absorption of B12 after gastric bypass surgery or in the setting of gastrointestinal diseases such as celiac or Crohn’s diseases. Some medications, particularly the diabetes treatment metformin or long-term use of acid-suppression, may cause decreased absorption.

If you have any of the symptoms listed above, particularly if you have some the listed risk factors, you should insist on being tested. The level of B12 can be measured in the blood, but there is a wide range of “normal” and many people who are deficient may be in the low normal range. One clue may be found looking at the size of your red blood cells. If you have a patient portal or a print-out of a recent CBC (complete blood count), look for a number described as the MCV. This is short for mean corpuscular volume and describes the size of the red blood cells.

Deficiency of B12 (or folic acid) typically leads to larger than normal red cells even before you become anemic. If your B12 level is below 200, you are deficient. If It is 200 to 300, you may be, even though the lab will list anything above 200 as normal. If your symptoms may suggest deficiency and your blood level is “low normal,” ask for further testing. This is not difficult. Another blood test, for methylmalonic acid (MMA) is almost always elevated with B12 deficiency. Be persistent. Ask to be tested: The testing is neither risky nor terribly expensive. The consequences of missing B12 deficiency can be severe.

Edward Hoffer is an internal medicine physician and author of Prescription for Bankruptcy: A doctor’s perspective on America’s failing health care system and how we can fix it. He blogs at What’s wrong with health care in America?

Image credit: Shutterstock.com

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