In a statement, athletic director Fred Glass said he respected Miller's decision and credited Miller for leaving the program in good shape. The school provided no additional details about Miller's health.
Last season, Miller, a 55-year-old Pennsylvania native, led the Hoosiers to a single-season record-tying 21 wins and the school's first postseason appearance in five years. Indiana won three games in the WNIT, its most in a single postseason tourney.
Glass appointed Miller's top assistant, Curtis Lloyd, interim head coach until the school finds a replacement.
Miller was 290-124 in 13 seasons, winning eight Mid-American Conference titles in 11 seasons at Bowling Green before taking the Indiana job.
