<prompt> In blood, bilirubin is withProteinSteroidVitaminCarbohydrates  <response>: Bilirubin formed by the destruction of RBCs is free or unconjugated bilirubin.It is lipid soluble and bound to albuminprotein conjugation,which prevents its excretion by the kidneys in urine. Ref.Text book of physiology by AK Jain 7th edition page no.79 