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Vitamin B12 Deficiency

Sahil Mullick, MD and Robin S. Chirackal, MBBS Reviewed 06/2020
 


BASICS

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

  • Cobalamin is critical for central nervous system myelination and normal functioning.

  • Deficiency can cause ...

DIAGNOSIS

Symptoms and physical exam findings: 
  • Asymptomatic patients may be diagnosed by the incidental finding of anemia or an elevated mean corpuscular volume (MCV) during routine testing or evaluat...

TREATMENT

MEDICATION

  • Parenteral cyanocobalamin replacement recommended in patients with severe neurologic symptoms: IM cyanocobalamin

    • 1,000 μg/day for 7 days, then

    • 1,000 μg weekly for 4 weeks, then

    • 1,000 ...

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Patient Monitoring

  • Hematologic

    • Reticulocytosis in 1 week

    • Rise in hemoglobin beginning at 10 days; usually will return to normal in 6 to 8 weeks

    • Monitor potassium in p...

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). pi...

ADDITIONAL READING

Langan RC, Goodbred AJ. Vitamin B12 deficiency: recognition and management. Am Fam Physician.  2017;96(6):384–389. 

CODES

ICD10

  • E53.8 Deficiency of other specified B group vitamins

  • D51.0 Vitamin B12 defic anemia due to intrinsic factor deficiency

  • D51.3 Other dietary vitamin B12 deficiency anemia

  • D51.1 Vitamin B12 defic...

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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