The 39-year-old, Germany's only Tour de France winner in 1997, was found guilty of doping in 2012 and he subsequently admitted to having had contact with Spanish sports doctor Eufemiano Fuentes, who was at the centre of the Operacion Puerta doping case.
Ullrich has now gone further by revealing that he also "received treatment" from Dr Fuentes.
"Almost everybody back then took performance-enhancing substances," he told Focus magazine.
"I didn't take anything which the others were not taking.
"For me, betrayal only begins when I gain an advantage, but that was not the case. I just wanted to ensure equal opportunities."
Ullrich's doping admission comes after his long-term rival Lance Armstrong conceded that he too had used performance-enhancing drugs.
"We are both guilty," said Ullrich. "I am no better than Armstrong, but no worse either.
"The great heroes of old are now people with failings that we've got to come to terms with.
"I always knew that even Lance Armstrong would not get away with it."
Ullrich retired from competitive cycling in 2007, saying he had "never once cheated" during his career.
Investigations into alleged doping continued until he was found guilty in February 2012.
He did not contest the decision by the Court of Arbitration for Sport.