From what I know, they don't go too far back. Weed? Maybe 2-3 days tops. Other drugs may linger around for 3-5 days, alcohol is 24 hours or so. If you come back positive with something, they may pull hair or make you pee in a cup, those are more accurate and go back longer of course.
Thanks its been a lil over two weeks,but I've been flushinf out these last two weeks they didn't take my child or anything. He said he would get back to me. I thought results were instant