is vitamin b12 injection prescription only Compounded Cyanocobalamin (Vitamin B12) Vitamin B12 Injection: Energy Boost
Description
Older Adults : As people age, the ability to absorb B12 decreases, making older adults more susceptible to deficiency

Well, the answer depends on the reason you want to inject, and on the frequency and duration you plan to inject for

Crepin VF, Collins JW, Habibzay M, Frankel G

Milk, While vitamin B12 supplements are safe, mothers are advised not to take excessive amounts

This effect is related to the synthesis of lipids and myelin sheath of nerve fibers have to maintain functional integrity

doi:10.1146/annurev.nutr.19.1.357