So i have recently tried IVing heroin but i have ran into a problem. i cannot for the life of me actually register if im in a vein. i know that i was in a vein because blood would come out when i pulled the needle out but when i would try to register nothing would come up. i decided to just inject what i had, i felt no pain and there was no bump or anything to indicate i had missed, i did not get much of a high as the stuff was very low quality, i have tried other veins and have run into the same problem. i am using 31 gauge insulin needles and my only conclusion is maybe my blood is to thick. is registering 100% needed? or can i just inject without doing so and stop if i feel any pain.