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Vitamin B12 Deficiency

Sahil Mullick, FAAFP, MD and Aya Allam, MD Reviewed 04/2024
 

  • Vitamin B12 deficiency is related to inadequate intake or absorption of cobalamin.

  • Cobalamin is critical for central nervous system myelination, red blood cell production, immune cell cytogenesis and ...

DESCRIPTION

Normal vitamin B12 absorption and diet recommendations 
  • Vitamin B12 is a water-soluble vitamin present in animal-source foods and foods fortified with vitamin B12.

  • Dietary vitamin B12 (coba...

EPIDEMIOLOGY

Prevalence

  • National Health and Nutrition Examination Survey documented 6.9% and 15% prevalence of B12 deficiency in US adults respectively aged 51–70 and over 70 years  (2).

  • Morbidity incre...

ETIOLOGY AND PATHOPHYSIOLOGY

  • Decreased oral intake

    • Vegetarians and vegans: Vitamin B12 is found in animal source foods.

  • Decreased IF

    • Pernicious anemia (PA): can be associated with autoantibodies directe...

COMMONLY ASSOCIATED CONDITIONS

  • Gastric abnormalities: PA, gastritis, gastrectomy/bariatric surgery

  • Small bowel disease: malabsorption syndrome, ileal resection, IBD, celiac disease

  • Pancreatic insufficie...

DIAGNOSIS

  • Asymptomatic; incidental finding of anemia or elevated mean corpuscular volume (MCV).

  • Neuropsychiatric

    • Frequent: sensory polyneuritis, paresthesias, positive Babinski sign, weakness, gait unst...

TREATMENT

All individuals with documented vitamin B12 deficiency should be treated, unless there's a strong reason not to such as patient refusal or palliative care setting. 

GENERAL MEASURES

  • Repleting ...

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Patient Monitoring

  • Hematologic

    • Reticulocytosis in 1 week

    • Hemoglobin will usually return to normal in 6 to 8 weeks

    • Monitor potassium in profoundly anemic patients.

  • Neur...

REFERENCES

1
Layden AJ, Täse K, Finkelstein JL. Neglected tropical diseases and vitamin B12: a review of the current evidence. Trans R Soc Trop Med Hyg. 2018;112(10):423-435. doi: 10.1093/trstmh/try078...

CODES

ICD10

  • D51 Vitamin B12 deficiency anemia

  • D51.3 Other dietary vitamin B12 deficiency anemia

  • D51.8 Other vitamin B12 deficiency anemias

  • D51.9 Vitamin B12 deficiency anemia, unspecified

  • E53.8 Deficiency ...

CLINICAL PEARLS

  • Vitamin B12 deficiency can coexist with other anemia; thus, MCV can be normal, decreased, or increased.

  • Common presenting symptoms include: fatigue, depression, falls, glossitis/loss of...

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