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Causes of vitamin B12 deficiency

 
, medical expert
Last reviewed: 04.07.2025
 
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Vitamin B12 deficiency, like folate deficiency, causes megaloblastic anemia. In true pernicious anemia, vitamin B12 absorption is impaired due to antibodies to the intrinsic factor. Unlike folate deficiency, vitamin B12 deficiency can cause spinal cord degeneration. Although megaloblastic anemia due to vitamin B12 deficiency can be treated with folate, this drug should never be prescribed for pernicious anemia, as it not only fails to improve the condition of patients with neurological disorders, but can even worsen it. Vitamin B12 concentration testing is used to diagnose macrocytic and megaloblastic anemia. It should be borne in mind that vitamin B12 deficiency develops slowly, over many years (up to 12 years after gastrectomy).

Diseases and conditions that may alter serum vitamin B12 levels

Increased concentration of vitamin B 12 Decreased concentration of vitamin B 12

Acute hepatitis

Hepatic coma

Chronic liver disease (liver cirrhosis)

Acute and chronic myelogenous leukemia

Erythromyelosis

Monocytic leukemia

Lymphocytic leukemia

Liver cancer metastases

Megaloblastic anemia

Addison-Biermer disease

Condition after gastrointestinal resection

Chronic inflammatory diseases and anatomical defects of the small intestine

Worm infestation

Alcoholism

Nutritional deficiency of B 12

Small bowel irradiation

Atrophic gastritis

Malabsorption

Vitamin deficiency in food (vegetarians)

Pregnancy

Taking cytostatics, aminosalicylic acid, aminoglycosides, ascorbic acid, phenytoin, phenobarbital

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