Indirect Bilirubin

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Latest Edit: Iva Lloyd, ND 2021-08-24 (EDT)

See Also Lab Tests

Indirect bilirubin, also known as unconjugated bilirubin refers to the protein albumin bound bilirubin that circulates in the blood on its way to the liver for conjugation. Elevated levels of this have been found to be associated with red blood cell destruction.[1],[2]

Patient Preparation

  • Fasting requirements vary among different laboratories
  • Factors which can cause increased levels:
  • Prolonged fasting
  • Factors which can cause decreased levels:
  • Exposure of sample to sunlight or bright artificial light at room temperature, high fat meal, air bubble and shaking of sample

Clinical Implications

Ranges: The following are the reference ranges for this lab. However, lab ranges can vary by laboratory and country.[2]

Standard U.S. Units Standard International Units
Conventional Laboratory Range 0.1-1.0 mg/dL 1.7-17.1 umol/L
Optimal Range 0.1-1.0 mg/dL 1.7-17.1 umol/L
Alarm Ranges > 1.8 mg/dL > 31 umol/L

High levels indicate:

  • RBC hemolysis
  • Gilbert's syndrome
  • Other conditions: trauma, large hematomas, hemorrhagic pulmonary infarcts, excessive red blood cell production pernicious anemia, severe lead poisoning)

Low leves indicate:

  • low levels or indirect bilirubin have no clinical significance

Associated Tests


  1. Pagana Kathleen D, Pagana Timothy J (1998) Mosby's Manual of Diagnostic and Laboratory Tests, Mosby, Inc
  2. 2.0 2.1 Weatherby Dicken, Ferguson Scott (2002) Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective, Bear Mountain