Doesn't hurt at all when it's going in - or even that day, it's the next 4-5 days that you feel it. I always jab into my glutes and when i was on it i could barely walk for about 4 days - and training legs was a complete no no. BUT i was jabbing 1ml at a time, i've been told since that you should water it down with other gear - i.e 0.25ml of test 400 in each 1ml of the other gear that your using. That way if your jabbing decca and sust every week you can easliy get a ml of 400 in you - just wish somebody told me first!!!!