Medical expert of the article
New publications
Causes of vitamin B12 deficiency
Last reviewed: 04.07.2025

All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
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 |