The 'American Reunion' actor - who checked himself into the Cirque Lodge rehab facility in Utah for a 30-day addiction programme after his second drink-driving arrest in 2010 - says his booze problem was so bad that he feared for his life.
He almost died from alcoholism. "I would have died, and I think about that every single day," the actor, 33, tells PEOPLE in an exclusive new interview.
After two DUI arrests and a jail sentence, the Nebraska-reared actor knew he had to turn his life around. Klein opens about his struggles for the first time.
"It got to the point where I was a fragile shadow of the young man that came into this business," he says. "Today, I'm the luckiest guy alive."
"It was nothing short of magic," says the actor, of his early stardom - something he quickly learned wouldn't last forever.
The actor is back on the big screen in the latest of the movie franchise, American Reunion, and says that he is now nearly 19 months sober. The 33-year-old actor shot to fame from his roles in Election and the 1999 hit movie American Pie.