The Welshman is set to make his comeback after a spell on the sidelines, while Raphael Varane remains unavailable due to injury.
The Welshman recently returned to regular training after a brief spell on the sidelines due to a calf injury and Ancelotti has now revealed that Bale will be included in the matchday squad for Monday's game at the Santiago Bernabeu.
"He will be included in the squad for the match tomorrow, but I have yet to decide if he’s going to play," the Madrid coach said at a press conference. "He has trained this week, he’s fine, he doesn’t have any problems. But we might wait a bit more so as to play him at peak condition."
Meanwhile, Ancelotti has made it clear that Raphael Varane still has some way to go until his comeback.
He added: "Raphael is still recovering. The knee is responding well. In 10 to 15 days he will start training with the team."
Varane last featured for Madrid on Nov. 9 in the league game against Real Sociedad.