UPDATE: A spokesperson for Octagon, the sports agency representing Michael Phelps, said in a statement to E! News that the Olympian "is entering himself into a six-week, inpatient program."
"While this has been an extremely difficult time for him, he is encouraged that this comprehensive program will help him focus on all of his life experiences and identify areas of need for long-term personal growth and development," the spokesperson said. "Michael takes this matter seriously and intends to share his learning experiences with others in the future."
USA Swimming Executive Director Chuck Wielgus added, "We fully support Michael's decision to place his health and well-being as the number one priority. His self-recognition and commitment to get help exhibit how serious he is to learn from this experience."
Olympic swimming champion Michael Phelps is taking a break to attend a "program" to seek help to "better understand" himself following his recent DUI arrest, his second in almost 10 years.
"The past few days have been extremely difficult," the 29-year-old tweeted early on Sunday. "I recognize that this is not my first lapse in judgment, and I am extremely disappointed with myself. I'm going to take some time away to attend a program that will provide the help I need to better understand myself."
"Swimming is a major part of my life, but right now I need to focus my attention on me as an individual and do the necessary work to learn from this experience and make better decisions in the future," added the most decorated Olympian in history, who has won 18 gold medals and 22 overall.
Phelps was arrested in Maryland on Sept. 30 for driving under the influence, excessive speed and crossing double lane lines inside a Baltimore tunnel. He later took to Twitter to say he understood the "severity" of his actions and takes "full responsibility."
"I know these words may not mean much right now but I am deeply sorry to everyone I have let down," said the Olympian, who is from the Baltimore area.
Police said he had driven his 2014 Land Rover at a speed of 84 mph in a 45 mph zone and failed several field sobriety tests.
In November 2004, Phelps, who was 19 at the time, was also arrested for DUI. He received 18 months of probation and a $250 fine and was required to deliver a presentation on alcohol awareness to students at three high schools, according to ESPN.
Phelps had announced his retirement after the 2012 Olympic Games in London, where he won four gold medals and two silver ones. He said earlier this year he would return to swimming and many speculate he will compete with the U.S. team during the 2016 Olympics in Rio, which would mark his fifth time taking part in the international competition. Nothing has been confirmed.
"I'm doing this for me," USA Today had quoted him as saying, regarding his career comeback. "If I don't become as successful as you think I would or should be, that's your own opinion. I enjoy being in the pool and sport of swimming and having fun with what I'm doing."
—Additional reporting by Lindsay Good