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Vitamin B12 participates in the synthesis of methyl groups required for the synthesis of purine and pyrimidine bases constituents of nucleic acids and in the production of the coenzyme methylcobalamin, which is necessary for methylation reactions

If you develop severe allergic reactions such as difficulty breathing, facial swelling, or widespread rash after a B12 injection, call 999 or go to A&E immediately, as these may indicate anaphylaxis, though this is extremely rare

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Yes, B12 is essential during pregnancy for the development of the fetal brain and nervous system