Vitamin B12 is an active pharmaceutical ingredient in the Vitamin B12 (Cyanocobalamin and Analogues) group (B03BA). The information below is compiled per regulator from the product labels on record, with direct links to the original documents.
CAOfficial regulatory label· revised May 19, 2026[1]
AND CLINICAL USE
Vitamin B12 Deficiency:
For vitamin B12 deficiency occurring in pernicious anemia with or without neurological complications. Other macrocytic, megaloblastic anemias where etiology suggests malabsorption of vitamin B12 such as following: gastrectomy, gastric carcinoma, megaloblastic anemia associated with such gastrointestinal disorders as sprue syndrome, blind loops and anastomoses and fish tapeworm.
Note:
In macrocytic megaloblastic anemia of pregnancy and sprue syndromes, cyanocobalamin may fail to produce satisfactory response, folic acid being indicated alone or in combination with cyanocobalamin. The injection is also suitable for use as the flushing dose in the Schilling (vitamin B12 absorption) test for pernicious anemia.
CONTRAINDICATIONS Vitamin B12 is contraindicated in patients who are hypersensitive to the vitamin or to cobalt, or to any ingredient in the formulation, including any non-medicinal ingredient, or component of the container. WARNINGS Patients who have early Leber's disease (hereditary optic nerve atrophy) have been found to suffer severe and swift optic nerve atrophy when treated with vitamin B12.
[1]Health Canada (DPD) · 00521515 · revised May 19, 2026
Information on this page is compiled from public regulatory records. Drugvu is not affiliated with any regulator or pharmaceutical manufacturer. This is not medical advice. Always consult a qualified healthcare professional.
Hypokalemia and sudden death may occur when severe megaloblastic anemia is treated intensively. Lack of therapeutic response may be due to infection, uremia, concomitant treatment with chloramphenicol or misdiagnosis. PRECAUTIONS A sensitivity history should be obtained from the patient prior to administration of vitamin B12; an intradermal test dose is recommended before vitamin B12 is administered to patients known to be sensitive to cobalamins.
Parenteral administration of cyanocobalamin is the required treatment for originally diagnosed and relapsed pernicious anemia with severe neurologic manifestations. Also in treatment of megaloblastic anemia associated with sprue, supplementation with folic acid is usually necessary and parenteral vitamin B12 may be required.
If a vitamin B12 deficiency is allowed to progress more than 3 months, permanent degenerative spinal cord lesions may occur, such lesions have been observed when folic acid is used as the sole hematopoietic agent. Vitamin B12 Page 4 of 8 Patients who have early Leber's disease (hereditary optic nerve atrophy) have been found to suffer severe and swift optic nerve atrophy when treated with vitamin B12.
Serum potassium concentrations should be monitored during early vitamin B12 therapy and potassium administered if necessary, since fatal hypokalemia could occur upon conversion of megaloblastic anemia to normal erythropoiesis with vitamin B12 as a result of increased erythrocyte potassium requirements.
Therapeutic response to vitamin B12 may be impaired by concurrent infection, uremia, concomitant treatment with chloramphenicol or misdiagnosis. Cyanocobalamin or hydroxocobalamin should not be administered intravenously (IV). Indiscriminated administration of vitamin B12 may mask the true diagnosis of pernicious anemia.
A dietary deficiency of only vitamin B12 is rare. Multiple vitamin deficiency is expected in any dietary deficiency.
May potentially cause vitamin B12 deficiency by decreasing gastric acid cleavage of vitamin B12 from food sources. This may be important in patients with low stores of vitamin B12 or in patients taking H2-antagonists for extended periods of time (>2 years).
Special Populations Pediatrics:
Benzyl alcohol contained in some products has been associated with toxicity in newborns. Toxicity appears to have resulted from administration of large amounts of benzyl alcohol (100 to 400 mg/kg daily). Products containing benzyl alcohol should be used cautiously in neonates, especially those who are receiving other benzyl alcohol containing medications.
Pregnant Women:
No adverse effects have been reported with ingestion of normal daily requirements during pregnancy.
Nursing Women:
Vitamin B12 is distributed into the milk of nursing women in concentrations that approximate the maternal blood vitamin B12 concentration. No adverse effects have been reported with intake of normal daily requirements during lactation.
ADVERSE REACTIONS Vitamin B12 is usually nontoxic even in large doses, however, mild transient diarrhea, polycythemia vera, peripheral vascular thrombosis, itching, transitory exanthema, feeling of swelling of the entire body, pulmonary edema and congestive heart failure early in treatment, anaphylactic shock and death have been reported following vitamin B12 administration.
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NOTE:
Contact your health professional if you need information about how to manage your side effects. The Canada Vigilance Program does not provide medical advice. DRUG INTERACTIONS Most antibiotics, methotrexate and pyrimethamine invalidate folic acid and vitamin B12 diagnostic microbiological blood assays.
Chloramphenicol may antagonize the hematopoietic response to vitamin B12. Hematopoietic response in such patients should be monitored. g. phenytoin, phenobarbital, primidone), para-aminosalicylic acid or excessive alcohol intake for longer than 2 weeks may impair the absorption of vitamin B12.
Vitamin C may destroy vitamin B12. Patients should avoid ingesting large amounts of vitamin C within 1 hour of oral vitamin B12 administration. DOSAGE AND AMINISTRATION Administration Cyanocobalamin is usually administered by IM or deep subcutaneous injection.
If the drug is administered subcutaneously, care should be taken to avoid injection […]