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Vitamin B12 Deficiency

Sahil Mullick, FAAFP, MD and Paramvijay Singh Dhalla, MD Reviewed 05/2023
 

  • Vitamin deficiency related to inadequate intake or absorption of cobalamin (vitamin B12)

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

  • Defi...

DESCRIPTION

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

  • Dietary vitamin B12 (cobalamin) bound to food is cl...

EPIDEMIOLOGY

Prevalence

  • Endemic area: Northern Europe, including Scandinavia; more common in those of African ancestry

  • Increasing recognition in breastfed-only infant populations with vitamin B12–defici...

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 directed...

COMMONLY ASSOCIATED CONDITIONS

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

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

  • Pancreatitis: pancrea...

DIAGNOSIS

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

  • Neuropsychiatric

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

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 (hyp...

REFERENCES

1
Lee SM, Oh J, Chun MR, et al. Methylmalonic Acid and Homocysteine as Indicators of Vitamin B12 Deficiency in Patients with Gastric Cancer after Gastrectomy. Nutrients. 2019;11(2):450.
2
Gree...

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.

  • For PA, cyanocobalamin must be lifelong.

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