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Vitamin B12 Deficiency Course

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Vitamin B12 (cobalamin) deficiency should be on your radar screen for several reasons. Prevention, early detection, and treatment of vitamin B12 deficiency are important public health issues, because they are essential to prevent development of irreversible neurologic damage which can impact quality of life. Although most health care providers already recognize the occasional person who presents with obvious signs and symptoms, they are far less likely to screen and diagnose the majority of patients who have a subclinical or mildly symptomatic vitamin B12 deficiency. Vitamin B12 deficiency is more common among older adults than many health care providers realize. Unpublished analysis at CDC of laboratory data from community-based samples of U.S. adults 51 years of age or older suggest about 1 (3.2%) of every 31 persons have serum vitamin B12, levels below 200 picograms per milliliter (pg/mL).

Vitamin B12 has profound effects on human health. Adequate body stores are essential for several crucial neurologic and hematologic functions. Delays in the diagnosis and treatment of vitamin B12 deficiencies can lead to development of severe, irreversible neurologic damage.

The clinical importance of vitamin B12 was established over 50 years ago when ingesting raw animal liver (the primary storage organ for vitamin B12) was found to be an effective treatment for pernicious anemia. Research has shown that the water-soluble vitamin B12 is required for the completion of several biochemical processes (see Figure 1).

The following five top things to remember about vitamin B12 in primary care practice summarize the implications of these and other cobalamin-related findings.

The top five things to remember about vitamin B12

1. Vitamin B12 deficiencies occur in adults 51 years of age or older at a frequency of 1 (3.2%) in every 31 persons, and manifest as serum vitamin B12 levels below the cutpoint of 200 pg/mL.

2. All patients with unexplained hematologic or neurologic signs or symptoms should be evaluated for a vitamin B12 deficiency. If found, the cause should be determined.

3. Today, megaloblastic anemia is most likely due to vitamin B12 deficiency and needs prompt evaluation. In the United States, folic acid fortification has made folate deficient megaloblastic anemia a very rare condition.

4. Although the body’s ability to absorb naturally occurring vitamin B12 decreases with age, most people can readily use the synthetic form of cobalamin.

5. All people 51 years of age and older should get most of their daily vitamin B12 through supplements containing vitamin B12 or foods fortified with vitamin B12.

This update has been prepared and organized to address four questions pertinent to primary health care providers:

  • Why should I be concerned about my patient’s vitamin B12 status?
    • Introduction
    • Case studies
    • Natural history and prevalence of vitamin B12 deficiencies
    • Manifestations of low vitamin B12 levels
  • Which of my patients are at high risk for a vitamin B12 deficiency?
    • Risk factors for a vitamin B12 deficiency
  • How do I detect and diagnose a vitamin B12 deficiency?
    • Screening patients
    • Detection and diagnosis
  • How should I manage a patient with evidence of a vitamin B12 deficiency?
    • Managing patients with evidence of a vitamin B12 deficiency
    • Preventing vitamin B12 deficiencies


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