The Welshman has largely impressed during his first season in Madrid, scoring 16 times and registering 15 assists in 34 games.
However, the 24-year-old has been criticised for a couple of under-par performances, which Ancelotti has claimed is normal.
"I think it's true that he's a bit in and out, but that's a characteristic of an attacker. You can't be a constant influence like a player such as Xabi Alonso, for example," he told reporters at a press conference.
Bale cost in the region of £80m from Tottenham Hotspur in the summer.