All of the Milwaukee runs were driven in by Carlos Gomez, who went 3-for-4.
Lohse (10-9) reached double digit wins in a season for the fifth time in his 13-year career. It was the ninth complete game he has worked in the majors, one in which he threw 111 pitches.
The Reds saw their lead for the second National League wild card berth reduced to 4 1/2 games over the streaking Washington Nationals, who won their seventh straight Friday.
Gomez had three singles which accounted for two runs in the first, one run in the third and two more in the seventh.
Mat Latos (14-6) gave up all five runs on seven hits in 6 2/3 innings.