Both players were hurt in Sunday's loss to the Denver Nuggets. Howard suffered a torn labrum in his right shoulder and Gasol was diagnosed with a concussion after he was hit in the face in the fourth quarter of the game.
The team didn't announce a timetable for either player's return.
Howard, who initially injured his shoulder last Friday, still tied a career high with 26 rebounds Sunday while playing 41 minutes. He is to have a further examination later in the week.
The Lakers are 15-18 on the season, 11 games behind the Los Angeles Clippers in the NBA Pacific Division. They are 11th in the Western Conference.
Los Angeles next plays road games Tuesday at Houston and Wednesday at San Antonio.