What bilirubin level indicates liver failure?

The normal bilirubin range in adults is less than 1 milligram per deciliter (mg/dL). Bilirubin levels above 1 milligram per deciliter (mg/dL) may indicate early liver problems. An increase in bilirubin levels of more than 20 milligrams per deciliter (mg/dL) may indicate a severe liver problem.