When the bilirubin-albumin complex (BIL:ALB) reaches the liver, the highly permeable hepatic circulation facilitates the complex to reach the sinusoidal side of the hepatocyte. The exact mechanism of unbound BIL uptake is unclear but may proceed like this. BIL in complex with ALB is reversible and a tiny fraction of of free BIL is present in plasma in equilibrium with BIL:ALB. Hence this free BIL may be taken up at a rate determined by its plasma concentration. As free BIL is taken up, more BIL is released from ALB and becomes available for uptake (Bhagavan & Ha 2015).