Reading the educational thread on injecting it says to aspirate the syrange by pulling the plunger back while the needle is in u to see if 1) air comes out and if so then inject away or 2) blood droplets come out then withdraw, switch needle and try again because u hit a blood vessel. My question is: is it necessary to do this everytime u inject no matter the injection site, quads, glutes, etc? I know when the doctor gives me a shot in shoulder say like a flu shot they just poke and inject. I dont remember seeing them aspirate the syrange to see if air bubbles come in or blood before they inject.