The Welshman has missed Madrid's last two games against Sporting Gijon and Bayern Munich due to a flare up of the muscles around where he suffered ligament damage in his right ankle earlier in the season.
Bale was forced off with the injury in the first leg of Madrid's eventual 6-3 aggregate win over Bayern just over a week ago.
Madrid host Barca with a three-point lead at the top of La Liga and with a game in hand.
Therefore, Real coach Zinedine Zidane is reluctant to rush Bale back into action with the first leg of the Champions League semi-finals less than two weeks away.
"When he came back he was desperate to be involved and now he has a small niggle that is preventing him from being fully fit," Zidane said ahead of the Bayern second leg.
"I hope it is nothing and in a few days he can be with us again."