How Long Does a B12 Shot Last In Your Body? Taking B12 for energy? The evidence says you're probably wasting your money. B12 is only powerful in one situation: when you're deficient. Not tired. Not run down. Not a bit low on A physician orders Schilling Test to be performed for a client suspected of having pernicious anemia. Order the steps below in completing this procedure. 1. Give oral radioactive vitamin B12 supplement before B12 Injections East Valley Urology Center of Arizona