I?ve been using I.V. what I thought was just white heroin for about 6 months now. Tried going to a subutex clinic about a month ago and turns out I tested negative for heroin and positive for fentanyl. I am planning on going into a detox center that accepts 24hr walk ins, however; you have to be in at least moderate withdrawal to be able to get admitted. I am now at exactly 36hrs and I still have zero symptoms. I was able to sleep all through the night and the only symptom I?ve had is just that I have no desire to eat. I?ve been doing about 16 packs a day so I guess that adds up to a little over a gram and a half. For the last 3 weeks, I haven?t even been getting high from using. Just staying well, but I?d never wait long enough to have withdrawal symptoms before the next time I used so I don?t really know when I?m supposed to start feeling withdrawals. I know that it?s impossible for me to just not have withdrawals at all so I guess I?m asking if anyone else has experience with iv fentanyl and withdrawal taking this long to set in? I?ve gotten off heroin before but that withdrawal set in after 12 hours so this is just really foreign to me. I tried looking up other posts about this and couldn?t find anything.