00:52 - Source: CNN
Michael Phelps opens up on alcohol use

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Michael Phelps talks about past alcohol use

The 18-time gold medalist admits he "doesn't know" if he's an alcoholic

Phelps is training for fifth Olympic Games at Rio 2016

CNN  — 

Michael Phelps, the most decorated athlete in Olympic history, has a checkered and well-publicized history with alcohol and drug use.

But is the 18-time Olympic gold medalist an alcoholic?

“I don’t know” was his candid response when the question was put to him. “I honestly don’t know.”

“I know I probably have moments where I have gone off the deep end where I shouldn’t.”

Read: What is Brazil worrying about with 100 days untl Rio 2016?

USA Swimming suspended Phelps for six months in 2014 for his second DUI arrest – the first coming 10 years earlier – and he was left out of the U.S. team for the 2015 World Championships.

Shortly afterward, Phelps attended a six-week, in-patient program to “provide the help I need to better understand myself.”

Read: Michael Phelps suspended by USA Swimming for six months

“I checked myself in because I think I was at a point in my life where something needed to change,” Phelps told NBC.

Read: Michael Phelps to ‘attend program’ after DUI charge

In 2009, a year after his historic eight-gold medal haul at the Beijing Olympics, a photo emerged of Phelps smoking marijuana, an incident he said made him realize who his real friends were.

The 30-year-old is training for what will be his fifth Olympic Games – Rio 2016.

“I want to retire how I want to retire – and I have a great opportunity to do that,” he said.