Bilirubin plasma level is the gold standard test for the diagnosis of jaundice. Usually the concentration of bilirubin in the blood must exceed 2–3 mg/dL for the coloration to be easily visible.

• Bilirubin plasma level is the gold standard test for the diagnosis of jaundice.
• Usually the concentration of bilirubin in the blood must exceed 2–3 mg/dL for the coloration to be easily visible.
• Laboratory findings consistent with the diagnosis of jaundice include:^[1]
  • An elevated concentration of serum total bilirubin. The upper limit of normal is >1 mg/dL or >1.3 mg/d in some laboratories.
  • Jaundice usually becomes clinically apparent when the serum total bilirubin concentration is greater than 2 to 3 mg/dL, but threshold for clinically apparent jaundice may vary among patients.
• Hyperbilirubinemia can be further categorized as conjugated or unconjugated:
  • Conjugated hyperbilirubinemia:
    • Serum conjugated bilirubin concentration >0.4 mg/dL (6.8 micromol/L).
    • Direct bilirubin >1 mg/dL (17 micromol/L) if the total bilirubin is <5 mg/dL (85 micromol/L), or more than 20 percent of the total bilirubin if the total bilirubin is >5 mg/dL (85 micromol/L).
  • Unconjugated hyperbilirubinemia:
    •  Conjugated bilirubin is <1 mg/dL (17 micromol/L) if the total bilirubin is <5 mg/dL, or less than 20 percent of the total bilirubin if the total bilirubin is >5 mg/dL (85 micromol/L).