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B12 and folate deficiency

Discuss B12 absorption?

B12 absorption depend on 5 factors-

  • Dietary intake
  • Acid-pepsin in the stomach to liberate B12 from binding to proteins
  • Pancreatic proteases to free B12 from binding to R factors
  • Secretion of intrinsic factor (IF) by the gastric parietal cells
  • Ileum

Discuss the causes of B12 deficiency?

  • Dietary deficiency- strict vegans
  • Stomach- pernicious anaemia, gastritis, gastrectomy
  • Small bowel- malabsorption, ileal disease/resection, blind loops
  • Pancreatic insufficiency
  • Drugs blocking absorption- metformin, PPI

Discuss the causes of folate deficiency?

  • Poor diet
  • Malabsorption
  • Drugs- methotrexate, trimethoprim, phenytoin
  • Increased demand- pregnancy, haemolysis

Discuss the diagnosis?

Serum B12 and folate
The serum folate concentration is a reflection of short-term folate balance. One hospital meal can normalize the serum folate in patients who are folate deficient. The red cell folate concentration is a more reliable indicator of tissue folate adequacy.  However, it is not entirely without its own problems of interpretation. Thus, the less expensive serum folate concentration should be obtained as an initial screening test.

Discuss the treatment?

Folic acid deficiency

Oral folic acid is 1 to 5 mg/day orally for 1-3 months until complete hematologic recovery occurs. The oral route is sufficient even in those with malabsorption. Vitamin B12 deficiency must be ruled out, and treated if present, before giving folic acid to a patient with megaloblastic anemia, since administration of folic acid may worsen neurologic complications of untreated vitamin B12 deficiency.

Vitamin B12 deficiency

IM 1 mg alternate days for 2 weeks and then 3 monthly


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