Biochemistry: How to Assess Vitamin B12 deficiency and its

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Assessment of Vitamin B12 Deficiency

Following methods are used to assess the Deficiency of Vitamin B12:

1. Serum B12:

  • It is quantitated by radioimmunoassay or by ELISA.

2. Schilling test:

  • Radioactive labelled (Cobalt-60) Vitamin B12, one microgram is given orally. 
  • In gastric atrophy cases, there is no absorption, hence the entire radioactivity is excreted in feces and radioactivity is not observed in liver region. 
  • If the cause is nutritional deficiency, there will be enhanced absorption. Then radioactivity is noted in the liver region, with very little excretion in feces.

3. Methyl malonic acid:

  • It is seen in urine.

4. FIGLU excretion test

5. Peripheral smear:

  • Peripheral blood and bone marrow morphology shows megaloblastic anemia.

6. Homocystinuria


  • If megaloblastic anemia is treated with folic acid alone, the anemia may improve, but associated neurological symptoms are aggravated. 
  • Hence all macrocytic anemias are generally treated with folate and Vitamin B12. 
  • Therapeutic dose of Vitamin B12 is 100 to 1000 microgram by intramuscular injections.

Daily requirement of Vitamin B12

  • Normal daily requirement is 1–2 mg/day. During pregnancy and lactation, this is increased to 2 mg/day. 
  • Those who take folic acid, should also take Vitamin B12. 
  • Elderly people are advised to take Vitamin B12 supplementation.

Dietary sources of Vitamin B12

  • Dietary Sources Vitamin B12 is not present in vegetables. 
  • Liver is the richest source. 
  • Curd is a good source, because lactobacillus can synthesize Vitamin B12.


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