Warren, the Sooners' leading scorer with a 16.2-point average, did not travel with the team for Saturday's 97-76 loss at Oklahoma State.
Coach Jeff Capel says he doesn't know how long Warren will be out because "it varies for each guy." The viral illness can linger for weeks and even months in some individuals.
Warren received votes for The Associated Press' preseason All-America team and had been considered a potential NBA draft prospect last year before returning for his sophomore season at Oklahoma.
He ranks 10th in the Big 12 in scoring.