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    HomeMedication GuideCyanocobalamin safety
    Vitamin B12 supplement

    Cyanocobalamin: What to Know Before You Take It

    Also known as Nascobal

    A patient-focused safety profile with information from public regulatory sources.

    Reviewed by the OmniRx Health clinical team•Last reviewed Jul 4, 2026

    In plain language

    What Cyanocobalamin is used for

    INDICATIONS AND USAGE Cyanocobalamin is indicated for vitamin B 12 deficiencies due to malabsorption which may be associated with the following conditions: Addisonian (pernicious) anemia Gastrointestinal pathology, dysfunction, or surgery, including gluten enteropathy or sprue, small bowel bacteria overgrowth, total or partial gastrectomy Fish tapeworm infestation Malignancy of pancreas or bowel Folic acid deficiency It may be possible to treat the underlying disease by surgical correction of anatomic lesions leading to small bowel bacterial overgrowth, expulsion of fish tapeworm, discontinuation of drugs leading to vitamin malabsorption (see Drug/Laboratory Test Interactions ), use of a gluten-free diet in nontropical sprue, or administration of antibiotics in tropical sprue. Such measures remove the need for long-term administration of cyanocobalamin. Requirements of vitamin B 12 in excess of normal (due to pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, hepatic and renal disease) can usually be met with oral supplementation. Cyanocobalamin Injection is also suitable for the vitamin B 12 absorption test ( Schilling Test ).

    Read before you decide

    Risks and precautions

    Risks and warnings

    WARNINGS Patients with early Leber's disease (hereditary optic nerve atrophy) who were treated with cyanocobalamin suffered severe and swift optic atrophy. Hypokalemia and sudden death may occur in severe megaloblastic anemia which is treated intensely. Anaphylactic shock and death have been reported after parenteral vitamin B 12 administration. An intradermal test dose is recommended before cyanocobalamin injection is administered to patients suspected of being sensitive to this drug. This product contains benzyl alcohol. Benzyl alcohol has been reported to be associated with a fatal "Gasping Syndrome" in premature infants. This product contains aluminum that may be toxic. Aluminum may reach toxic levels with prolonged parenteral administration if kidney function is impaired. Premature neonates are particularly at risk because their kidneys are immature, and they require large amounts of calcium and phosphate solutions, which contain aluminum. Research indicates that patients with impaired kidney function, including premature neonates, who receive parenteral levels of aluminum at greater than 4 to 5 mcg/kg/day accumulate aluminum at levels associated with central nervous system and bone toxicity. Tissue loading may occur at even lower rates of administration.

    Who should not take it

    CONTRAINDICATIONS Sensitivity to cobalt and/or vitamin B 12 is a contraindication.

    Medication review

    Cyanocobalamin drug interactions

    Check this against your full medication list in the Interaction Checker

    FDA safety data

    Most-reported side effects

    Based on 33,535 FAERS reports. Reports do not prove the drug caused the effect.

    fatigue 3,312nausea 2,734off label use 2,384headache 2,372pain 2,251diarrhoea 2,244drug ineffective 2,138dyspnoea 2,117vomiting 1,788asthenia 1,780arthralgia 1,772fall 1,714
    Explore full FDA safety data

    Regulatory record

    FDA recalls (3)

    Class IIITerminated · Apr 5, 2022

    Subpotent Drug: Out of Specification results for Assay

    Recalling firm: Aurobindo Pharma USA Inc.

    Class IITerminated · Mar 15, 2021

    CGMP Deviations: Intermittent exposure to temperature excursion during storage.

    Recalling firm: Cardinal Health Inc.

    Class IITerminated · Sep 27, 2012

    Lack of Assurance of Sterility: Glass vials may have finish fractures and glass particles.

    Recalling firm: Fresenius Kabi USA, LLC

    Common questions

    Patient questions

    What is Cyanocobalamin prescribed for?

    INDICATIONS AND USAGE Cyanocobalamin is indicated for vitamin B 12 deficiencies due to malabsorption which may be associated with the following conditions: Addisonian (pernicious) anemia Gastrointestinal pathology, dysfunction, or surgery, including gluten enteropathy or sprue, small bowel bacteria overgrowth, total or partial gastrectomy Fish tapeworm infestation Malignancy of pancreas or bowel Folic acid deficiency It may be possible to treat the underlying disease by surgical correction of anatomic lesions leading to small bowel bacterial overgrowth, expulsion of fish tapeworm, discontinuation of drugs leading to vitamin malabsorption (see Drug/Laboratory Test Interactions ), use of a gluten-free diet in nontropical sprue, or administration of antibiotics in tropical sprue. Such measures remove the need for long-term administration of cyanocobalamin. Requirements of vitamin B 12 in excess of normal (due to pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, hepatic and renal disease) can usually be met with oral supplementation. Cyanocobalamin Injection is also suitable for the vitamin B 12 absorption test ( Schilling Test ).

    What are the key warnings and safety precautions for Cyanocobalamin?

    WARNINGS Patients with early Leber's disease (hereditary optic nerve atrophy) who were treated with cyanocobalamin suffered severe and swift optic atrophy. Hypokalemia and sudden death may occur in severe megaloblastic anemia which is treated intensely. Anaphylactic shock and death have been reported after parenteral vitamin B 12 administration. An intradermal test dose is recommended before cyanocobalamin injection is administered to patients suspected of being sensitive to this drug. This product contains benzyl alcohol. Benzyl alcohol has been reported to be associated with a fatal "Gasping Syndrome" in premature infants. This product contains aluminum that may be toxic. Aluminum may reach toxic levels with prolonged parenteral administration if kidney function is impaired. Premature neonates are particularly at risk because their kidneys are immature, and they require large amounts of calcium and phosphate solutions, which contain aluminum. Research indicates that patients with impaired kidney function, including premature neonates, who receive parenteral levels of aluminum at greater than 4 to 5 mcg/kg/day accumulate aluminum at levels associated with central nervous system and bone toxicity. Tissue loading may occur at even lower rates of administration.

    Does Cyanocobalamin interact with other medications or foods?

    Cyanocobalamin has 2 documented drug interaction(s) and 0 food interaction(s) in clinical databases. Always provide your complete medication list to your clinician.

    This information is educational — not medical advice.

    This page is provided for general educational purposes and summarizes publicly available data from sources such as the U.S. Food & Drug Administration. It is not a substitute for the judgment of a licensed clinician and should not be used to start, stop, or change any medication. It may be incomplete or out of date, and individual circumstances vary. Always talk with your prescriber or pharmacist about your specific medications and health conditions. If you think you may have a medical emergency, call 911.

    Have medication questions?

    A licensed OmniRx provider can review your health history and medication list. Availability and treatment options are determined individually.