The latest suspension of Mejia, who last May was given an 80-game ban after testing positive for Stanozolol, is effective immediately, MLB said in a statement.
In nine appearances out of the Brewers bullpen this season Mejia allowed 15 hits and seven earned runs in 11-1/3 innings of action. Mejia owns an 8.32 earned run average in 66 career major-league innings.
The Brewers, who lead the National League Central division, placed Mejia on the 15-day injured list in August and last week transferred him to the 60-day IL.
Brewers General Manager Matt Arnold said in a separate statement the team "fully support MLB's Joint Drug Prevention and Treatment Program and share in the goal of eliminating performance-enhancing substances from our game."