Bayern Munich top the standings following their 2-1 win over Freiburg on Saturday with Schalke 04 two points adrift in second place after beating VfB Stuttgart by the same score.
Leverkusen's emphatic win put an end to any crisis talks after the team had failed to win their last three matches and had also suffered their first defeat of the season last week against Nuremberg.
"The team really improved in the second half, calmed down and became more accurate and we deserved to win. We reacted very well after the equaliser," Leverkusen coach Jupp Heynckes told reporters.
Kiessling, who has almost certainly booked a place in Germany's World Cup squad with a stunning season so far, gave his team the lead in the 22nd minute, against the run of play, when he broke free and beat keeper Frank Rost with a well-placed low drive.
Adler has been named as the starting Germany keeper but was far from consistent for the third straight game, after errors in Germany's friendly with Argentina and against Nuremberg in the league last week.
In Sunday's other match, Werder Bremen beat hosts Hoffenheim 1-0 courtesy of Claudio Pizarro's 11th goal of the season, to move up to 42 points, one behind Hamburg who are fifth, and remain in the hunt for a European spot.
