Shields won that particular fight with a decision, with all three judges scoring the fight 30-27, sending his MMA career to 28–6–1. It hasn’t been revealed yet if the UFC will reverse the score Shields was busted.

“To my friends, fans and the UFC: Prior to my professional bout at UFC 150 in Denver, Colorado, I used a substance prohibited by Colorado Boxing Commission rules. This was a mistake that I fully regret. I have shared this issue with my family and the UFC and I have apologized to them and now I also apologize to you, the fans,” the 33 year old fighter said in a statement.

“I promise this will never occur again in my fighting career. I accept the Boxing Commission’s decision for a six-month suspension, which will expire in February. I ask that you accept my apology. I will be back fighting soon, and hope that the fans of MMA will support me until that time.”

There were no mentions of what banned substance he used.