The Welshman, who featured in Madrid's 2-1 defeat to Barcelona at Camp Nou, has struggled with fitness issues since arriving at the Bernabeu in the summer.
"It's true that in the last few games he hasn't done extraordinary things, but a player who arrives at a new team, in a new culture, needs time to adapt," Ancelotti told Spanish radio station Cadena Cope.
"The problem the player has is of adaptation. It's not the same to play in Spain as in England."
Bale has yet to complete an entire match for Madrid.