"I had a problem and I needed a quick solution," McMahon, 38, was quoted as saying in a television programme on Sunday. "The consequence is my retirement."
Last week, McMahon admitted using EPO "for therapeutic reasons, and in a very small dosage" but said she had not used drugs at the 2000 Sydney Olympic Games where she won triathlon's first Olympic gold medal.
A trained biochemist and mother of three, McMahon had been training for next year's world championships when she tested positive in an out-of-competition test at her home in central Switzerland last month.
