The prescribing information for cyanocobalamin injection lists adverse reactions by category, and its generalized category names anaphylactic shock and death. The label statements cited here do not list symptoms for which to call a clinician. A MedlinePlus health topic page on anaphylaxis says to call 911 if someone is having a serious allergic reaction.
Adverse reactions the label lists
Under adverse reactions, the label lists:
- Generalized: anaphylactic shock and death have been reported with administration of parenteral vitamin B12.
- Cardiovascular: pulmonary edema and congestive heart failure early in treatment; peripheral vascular thrombosis.
- Hematological: polycythemia vera.
- Gastrointestinal: mild transient diarrhea.
- Dermatological: itching; transitory exanthema.
- Also listed: feeling of swelling of entire body.
The lines quoted here do not say which patients these reactions were reported in.
The Nascobal (cyanocobalamin nasal spray) label, not the injection label, states that the most common adverse reactions (4% or more) were infection, headache, glossitis, paresthesia, asthenia, nausea and rhinitis. That list is for a nasal spray and is not a list for an injection.
Reports of acne and other symptoms
A single case report describes a young woman treated with multiple daily doses of 1 mg of cyanocobalamin for severe pernicious anemia (the case details do not state the route, and her B12 level is not given here). After a total dose of 12 mg, she developed acne, palpitations, anxiety, akathisia, facial ruddiness, headache and insomnia, and improved two weeks after stopping the drug. A single case report cannot show cause and effect.
A review of acne related to dietary supplements states that a number of dietary supplements have also been linked to acne, including those containing vitamins B6/B12, iodine and whey. The supplements named contain B6/B12, not B12 alone, and the people, form and dose are not given here. "Linked" describes an association, which does not show that B12 caused acne.
What the label says about allergy, eye disease, alcohol and kidney function
The label describes the product as a sterile solution of cyanocobalamin for intramuscular or subcutaneous injection. The table sets out what the label says on four subjects. It is not a checklist, and the label statements cited do not say what to tell a clinician.
| Subject | What the label says |
|---|---|
| Sensitivity | The label lists sensitivity to cobalt and/or vitamin B12 as a contraindication. |
| Early Leber's disease | The label warns that patients with early Leber's disease (hereditary optic nerve atrophy) who were treated with cyanocobalamin suffered severe and swift optic atrophy. |
| Heavy alcohol intake | The label says colchicine, para-aminosalicylic acid and heavy alcohol intake for longer than 2 weeks may produce malabsorption of vitamin B12. |
| Impaired kidney function | The label warns that the product contains aluminum that may be toxic, and that aluminum may reach toxic levels with prolonged parenteral administration if kidney function is impaired. |
Serious allergic reactions and emergency calls
The label warns that anaphylactic shock and death have been reported after parenteral vitamin B12 administration and recommends an intradermal test dose for patients suspected of being sensitive to the drug.
A MedlinePlus health topic page states that anaphylaxis is a serious allergic reaction. It adds that anaphylaxis can begin very quickly and that symptoms may be life-threatening. It also says that if someone is having a serious allergic reaction, call 911.
That page concerns anaphylaxis in general. The sentences cited do not name B12 injections.
What this does not tell you
The label lists reactions without giving figures for how often they occur, and the nasal spray percentage belongs to that product. The case report and the acne review cannot show that B12 caused the symptoms described. None of the sources cited sets out which symptoms after a B12 injection call for contacting a clinician, and a licensed provider decides whether a symptom is related to an injection. A symptom that appears on one of these lists does not by itself show that an injection caused it, and a symptom that is missing from them does not show that it did not.
The label statements above come from an approved cyanocobalamin injection. An FDA page states that compounded drugs are not FDA-approved, which means FDA does not verify the safety, effectiveness or quality of compounded drugs before they are marketed. Another FDA page encourages people with an adverse reaction to a compounded medication to report it to their health care professional and directly to FDA.