How long will heroin stay in your system?
Totally depends on the length of use and the amount used. If you've been using for an extended period of time, it can take up to a week for withdrawals of any sort to be gone. The main withdrawal will start within 24 hours. If you just use one time, which is rare, you won't withdraw but it will take a good 2-3 days to be clean again depending on your body fat percentage and metabolism.
I've struggled with this addiction for 6 years and can only say one thing to anyone about it.... DON'T DO IT. It will take your soul along with any future you have. That is not an overstatement.
I've been sober for a month now and I still struggle hard with it. Thank God I have a good support system and the clarity/knowledge to know that if I go back I can officially kiss any possible future of mine good-bye. I pray for everyone in the struggle and that you can just stay away from it altogether.
Good luck to all, you're strong enough to change, you just have to make the decision, truly, for yourself. God Bless