Skip to content

Bilirubin, Unconjugated and Conjugated, Serum/Plasma — Substance Concentration

Published: August 9, 2026Updated: August 16, 2026

Measures conjugated and unconjugated bilirubin in serum or plasma to help evaluate causes of jaundice and liver or blood disorders.

Quick summary

["This test helps determine whether an elevated bilirubin level is mainly associated with liver dysfunction or increased blood-cell breakdown."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
33899-6
Short code
Bilirub Conj+Unconj SerPl-sCnc
Synonyms
Bilirub Conj+Unconj SerPl-sCnc
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

This test measures the amounts of conjugated and unconjugated bilirubin in your blood. Bilirubin is a yellow pigment produced when the body breaks down the oxygen-carrying part of red blood cells.

Why might I need this test?

Doctors may order this test when you have jaundice, dark urine, pale stools, itching, or unexplained changes in liver blood tests. It can help evaluate liver disease, bile duct problems, and increased red blood cell breakdown.

How is the test performed?

A blood sample is drawn from a vein and analyzed in a laboratory. The laboratory reports the conjugated and unconjugated bilirubin amounts, which may be considered together with your other test results.

How do I prepare for the test?

Fasting is usually not required, but follow your clinician's instructions. Tell the laboratory and clinician if you are pregnant or breastfeeding, because pregnancy can affect bilirubin levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated unconjugated bilirubin may occur when red blood cells are being broken down faster than normal or when the liver is not processing bilirubin efficiently. Elevated conjugated bilirubin may suggest liver inflammation, impaired bile excretion, or a bile duct blockage. Results must be interpreted with symptoms, medical history, and other laboratory tests.

Short name

Fractionated Bilirubin

Frequently asked questions

What is the difference between conjugated and unconjugated bilirubin?
Unconjugated bilirubin has not yet been processed by the liver. Conjugated bilirubin has been processed by the liver and is ready to be excreted into bile.
Does this test diagnose a specific condition?
No. The results help identify possible patterns of liver dysfunction, bile flow problems, or increased red blood cell breakdown, but additional testing is often needed to determine the cause.
Do I need to fast before this test?
Fasting is generally not required for fractionated bilirubin testing. Follow any specific instructions from your clinician, particularly if the test is being ordered as part of a larger panel.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy