I have never used meth but my husband has. I realized he was using when he wouldn't sleep for up to 3 days at a time and when he did sleep his entire body would twitch randomly. I also noticed large bruises and scabs on his body. I began to find broken pieces of glass all through the house. He was breaking his "pipes" after he smoked. After he started using he had 2 car accidents within a month. I also realized that he was using when his own behavior and attitude changed. He used to be very sweet and loving and funny! Then all of a sudden he became angry and distant. He would scream at me all the time for no reason! He had no interest in anything of the things he used to. When I confronted him about it he denied everything to the end.