Vitamin B12 (synonyms: cobalamin, extrinsic factor) is a vital dietary component of the vitamin B complex. If it is not supplied to the body, deficiency symptoms occur (hypo-/avitaminosis). Vitamin B12 is absorbed in the small intestine after it binds to intrinsic factor (IF) in the stomach. It cannot be absorbed in the free form. However, it also occurs naturally in the body but cannot be synthesized by it. Vitamin B12 is water soluble. It is stored in the liver. The storage covers the need for several years. It is found mainly in animal foods. The main function of vitamin B12 is as a coenzyme in many different metabolic processes, such as carbohydrate and fat metabolism, as well as nucleotide (DNA synthesis) and nucleic acid metabolism. In addition, it is important for the function of nerve cells as well as blood formation (it controls the absorption of folic acid into erythrocytes – red blood cells). The following symptoms may occur with a vitamin B12 deficiency:
- Anemia, megaloblastic (anemia).
- Anorexia nervosa (anorexia)
- Ataxia (gait disorders)
- Funicular myelosis (synonym: funicular spinal disease) – demyelinating disease (degeneration of the posterior cord, lateral cord, and a polyneuropathy/diseases of the peripheral nervous system affecting multiple nerves) caused by vitamin B12 deficiency; symptomatology: motor and sensory deficits that may worsen to paraplegia; encephalopathy (pathological conditions of the brain) of varying degrees.
- Gastritis (inflammation of the gastric mucosa).
- Glossitis (inflammation of the tongue)
- Sensory disturbances
The procedure
Material needed
- Blood serum
Preparation of the patient
- Not necessary
Disruptive factors
- The blood sample must be protected from light
Standard values
| Value in ng/l | Value in pmol/l | |
| Normal range | > 300 | 221,4 |
| Deficiency | < 200 | 147,6 |
| Surplus | > 1.100 | 811,8 |
Indications
- Suspected anemia (anemia of the blood)
Interpretation
Interpretation of increased values
- Administration of vitamin B12
- Hepatitis (inflammation of the liver)
- Liver metastases
- Leukemia (blood cancer)
- Osteomyelosclerosis – replacement of the hematopoietic tissue by connective tissue.
- Polycythaemia vera – pathological multiplication of blood cells (particularly affected are: especially erythrocytes/red blood cells, to a lesser extent also platelets (blood platelets) and leukocytes/white blood cells); stinging itching after contact with water (aquagenic pruritus).
Interpretation of decreased values
- Alimentary (nutritional)
- Inadequate intake, especially older women or men (≥ 65 years), respectively.
- Long-term malnutrition and malnutrition, such as vegans, strict vegetarians.
- Malabsorption (disorder of absorption)
- “Food-cobalamin malabsorption”, for example in hyperchlorhydria, gastritis / Helicobacter pylori infection, under acid suppression therapy.
- Chronic inflammatory bowel disease such as Crohn’s disease or ulcerative colitis.
- Short bowel syndrome – malabsorption after extensive small bowel resection – partial removal of the small intestine.
- Infection with lamblia (small intestinal parasites).
- Celiac disease (gluten-induced enteropathy; chronic disease of the mucosa of the small intestine (small intestinal mucosa), which is based on hypersensitivity to the grain protein gluten).
- Maldigestion (disorder of digestion).
- Decreased ability to digest protein / disruption of the release of the vitamin from food.
- Pancreatic insufficiency – inability of the pancreas to produce sufficient digestive enzymes.
- Diseases
- Absence of intrinsic factor (in pernicious anemia or after gastrectomy).
- Chronic atrophic gastritis (gastritis).
- Autoimmune gastritis
- Parietal cell antibodies (PCA) → cause destruction of gastric parietal cells → decreased acid secretion (achlorhydria) and intrinsic factor deficiency → decreased absorption of vitamin B12, resulting in pernicious anemia.
- Inborn errors of metabolism (in transcobalamin deficiency, Imerslund-Gräsbeck syndrome).
- Increased consumption or loss
- Dysbiosis (disorders in the flora of the small intestine such as bacterial overgrowth).
- Increased consumption (in bacterial overgrowth or fish tapeworm infestation, in HIV infection, multiple sclerosis).
- Other causes
- Severe chronic liver disease
- Severe chronic kidney disease
- Medication
- Omeprazole and metformin (decrease absorption of vitamin B12).
Other notes
- The normal requirement of vitamin B12 in women as well as men is 4.0 µg/d, the reserves last for 1-2 years.
Attention. Note on the state of supply (National Consumption Study II 2008)21% of men and 50% of women aged 35-50 years do not reach the recommended daily intake (for more see “National Consumption Study (nutritional situation)”.