B12 Injection Dosage and Frequency: 7 Essential Guidelines for Adults Liv Hospital For those taking injectable B12, how often is your level tested? : r B12_Deficiency B12 Injections Explained Vitamin B12 plays a key role in energy, metabolism, and nerve function. Injections allow direct absorptionespecially helpful for those with low levels or absorption issues. DM to book Vitamin B12 plays an important role in energy metabolism, nervous system function, and red blood cell production. For some individuals, Vitamin B12 injections may be used as part of overall wellness