Bioelectrical Impedance Analysis or Bioimpedance Analysis (BIA) is a diagnostic tool that accurately assesses your complete body composition - the measurement of body fat in relation to lean body mass as well as cell membrane integrity, intra and extracellular water, and other specific aspects of body composition.IA also provides a measurement of fluid and body mass that can be a critical assessment tool for your current state of health. BIA also serves to measure your progress as you work to improve your health.