It hurts the most when you quit taking it and shrink. IMO, the pain means it's working to a certain extent. I am doing some Sust right now (300mg/ml) and it has BA and EO in it - it is painless - almost completely. Out of 15 injects so far only 2 have hurt, and they were nothing more than a pricked nerve/vein/etc. I shoot it in my quads, and shoot it every 3rd day