LOS ANGELES » UFC veteran Chael Sonnen retired from mixed martial arts a day after confirming he failed a recent drug test.

Sonnen’s bout with Vitor Belfort at UFC 175 in Las Vegas next month was scrapped after Sonnen tested positive for two banned substances.

The 37-year-old Sonnen (28-14-1) says he took the substances to ease his transition off testosterone replacement therapy, which was banned by the Nevada Athletic Commission earlier this year.

Sonnen has lost three of his last four fights, including UFC title shots against Anderson Silva and Jon Jones.

Sonnen lost all three of his career UFC championship fights. He made his UFC debut in 2005.

He announced his retirement Wednesday on Fox Sports, where he serves as a UFC commentator.