What are side effects of vitamin B12?

Side effects of vitamin B12 are not common. It is possible to develop an allergy to vitamin B12; symptoms of a B12 allergy may include skin rash. Other side effects that have been reported include anxiety, back pain, cough, diarrhea, dizziness, nose bleed, fever, headache, infection, malaise, nausea, itching, rash (unspecified), runny nose, sinusitis, and vomiting.

If you have any bothersome side effects after starting B12 treatment, you should talk to your doctor.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.