Commonly used injection sites for B-12 injections are the upper arm, buttocks, outer hip and thigh, states Amino Pharmaceuticals. Injection location depends on the age of the recipient, as well as who is administering the shot.
Upper arm shots are given to young or middle-aged adults when the dose is less than one milliliter, notes Amino Pharmaceuticals. Those who self-administer shots typically use the thigh muscle or outer hip, as it contains no major blood vessels. This area is also used for infants and small children. The buttocks, also called the dorsogluteal site, is located close to the sciatic nerve as well as to major blood vessels, and thus should only be used by professionals.