What does it measure?
This is the unconjugated form that circulates before liver processing, usually carried by albumin. Many laboratories calculate it by subtracting direct bilirubin from total bilirubin. Because it is often calculated, the accuracy of both measured components affects the result. [1]
Before reading the calculation
- Inputs
- Usually calculated as total bilirubin minus direct bilirubin from the same sample.
- Context
- Retain both measured results and mention illness or known Gilbert syndrome.
What can the result mean?
An increase may occur when more red blood cells are being broken down or when the liver processes bilirubin more slowly. Gilbert syndrome is a common, usually harmless example of reduced processing. A low indirect result generally has no special clinical significance. [1]
Usually calculated as total bilirubin minus direct bilirubin from the same sample.
- Context
- Retain both measured results and mention illness or known Gilbert syndrome.
When is it useful, and how is it read?
A predominantly indirect rise prompts questions about red-cell breakdown, bilirubin uptake, and liver conjugation, including Gilbert syndrome in the right setting. Hemoglobin and other hemolysis findings may help when red-cell breakdown is suspected; the bilirubin result alone does not diagnose hemolysis. [1] [3]
What can affect it?
Blood counts and markers of red-cell breakdown may be useful if anemia is suspected. The other liver tests help distinguish patterns. Fasting, illness, and dehydration can bring out a bilirubin rise in people with Gilbert syndrome, but that diagnosis should not be assumed from one number. [1]
Indirect bilirubin is often a calculated result
Many laboratories obtain indirect bilirubin by subtracting direct bilirubin from total bilirubin. It is therefore linked to the accuracy of both measurements, rather than always being a separate assay. [1]
Questions you might have
Is indirect bilirubin a separate blood draw?
Usually not. It is commonly calculated from the two measured bilirubin results. [1]
Does high indirect bilirubin always mean red-cell breakdown?
No. Reduced liver processing, including Gilbert syndrome, is another possibility. The blood count and other liver results help distinguish causes. [1]
What comes next?
Ask your clinician whether the rise is isolated and whether previous results show the same pattern. A targeted review may avoid unnecessary repeat testing while still checking important causes. New yellowing of the eyes or skin deserves assessment, particularly if accompanied by other symptoms. [1]
Is this an isolated processing difference, or is there evidence of increased red-cell breakdown?
The reference interval and units on your report are part of understanding your result. Understand units, reference intervals, and treatment targets.
Sources & references
Medical references & original research
Books we consulted
References that informed our explanations of the test and its context.
- Pagana KD, Pagana TJ, Pagana TN. Mosby’s Diagnostic and Laboratory Test Reference. 14th ed. Elsevier; 2019.
Practical-section sources accessed: .
For general health education. Interpreting your result and deciding on tests or treatment requires your health context and a qualified clinician.
