B12 injections . There are no benefits to getting B12 injections unless you have a deficiency and you are not able to absorb it thru the gut . Some times Vegans can become deficient because they do not eat animal fat and they would have to get injections . I have heard of psychiatrists giving B12 injections during periods of increased stress ; not sure why !! Perhaps to calm the nerves . Hope this helps .
Nothing over oral. unless you have some type of severe B12 deficiency or pernicious anemia.