We sought to develop an oral treatment for unconjugated hyperbilirubinemia. In the Gunn rat model of unconjugated hyperbilirubinemia, dietary supplementation with the lipase inhibitor orlistat (Orl) or with calcium phosphate (CaP) decreases plasma unconjugated bilirubin (UCB) levels. We determined whether Orl, CaP, or their combination is superior to phototherapy, the conventional treatment, and whether the effects of Orl and CaP are influenced by dietary fat content. Gunn rats were treated with Orl (200 mg/kg chow), CaP (20 g/kg chow), Orl ؉ CaP, or continuous phototherapy (19 W/cm 2 /nm) during a low-fat (LF) diet (13 energy%) or high-fat (HF) diet (35 energy%). Plasma UCB and fecal fat excretion were measured before, during, and/or at the end of treatment. Orl treatment for 2 weeks (HF diet) reduced plasma UCB concentrations similar to phototherapy (؊34% and ؊28%, respectively); the combination of both was more effective than either treatment alone (؊48%; P < .001). After 3 weeks of a HF diet, plasma UCB was 46% lower compared with the LF diet (P < .001). Plasma UCB concentrations were negatively correlated with fecal fat excretion (r ؍ ؊0.96; P < .001). Irrespective of dietary fat content, 3 weeks of combined treatment (Orl ؉ CaP) decreased plasma UCB by approximately 50% (P < .01) and was more effective than phototherapy (P < .05) at the intensity provided. C rigler-Najjar disease is characterized by a permanent unconjugated hyperbilirubinemia due to absent (type I) or decreased (type II) activity of the hepatic enzyme bilirubin-UDP-glucuronosyltransferase. 1 Severe unconjugated hyperbilirubinemia can lead to bilirubin encephalopathy, kernicterus, and death. 2,3 Phenobarbital treatment can usually control unconjugated hyperbilirubinemia in Crigler-Najjar type II patients via residual enzyme induction. 4,5 Phenobarbital is not effective in Crigler-Najjar disease type I, however, so these patients have to undergo daily phototherapy, which has considerable disadvantages. Phototherapy becomes less effective with age, probably due to skin alterations, 6,7 a decrease in the surface area to body mass ratio, 8 and a diminishing compliance to the intensive phototherapy regimen, which may take up to 12 hours per day. 6 To prevent irreversible brain damage due to kernicterus, many patients with CriglerNajjar disease type I undergo liver transplantation in their second decade. 9,10 We sought to develop an alternative treatment for unconjugated hyperbilirubinemia based on oral administration and with equal or higher efficacy than phototherapy. The oral treatment strategy used in the present study is based on reducing the reabsorption of UCB 11,12 through intestinal capture. Reabsorption of UCB can contribute substantially to the pathogenesis