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Conjugated Bilirubin, Serum/Plasma — Mass Fraction

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

Measures the conjugated, or direct, form of bilirubin in a blood sample to help evaluate liver function and the cause of jaundice.

Quick summary

["This blood test helps assess how the liver processes bilirubin and can help identify jaundice caused by liver disease or bile duct blockage."]

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

Key facts at a glance

LOINC
34442-4
Short code
Bilirub Conj MFr SerPl
Synonyms
Bilirub Conj MFr SerPl
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?

Conjugated bilirubin, also called direct bilirubin, is the form of bilirubin that has been processed by the liver. This test measures the amount of conjugated bilirubin relative to the total bilirubin in a serum or plasma blood sample.

Why might I need this test?

Your clinician may order this test as part of a liver function evaluation or to help investigate jaundice, which can cause yellowing of the skin or eyes. It may also be used to help distinguish between causes of jaundice involving the liver or bile ducts.

How is the test performed?

A blood sample is drawn from a vein and analyzed in the laboratory. The result is usually considered along with your total bilirubin and other liver tests, because the conjugated portion alone does not provide the complete picture.

How do I prepare for the test?

Fasting is generally not required for this test, although your clinician may give specific instructions if it is being ordered with other tests. Tell your clinician about medicines, supplements, pregnancy, or recent liver or gallbladder problems that could affect the result.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Conjugated bilirubin

Frequently asked questions

Is conjugated bilirubin the same as direct bilirubin?
Yes. Conjugated bilirubin is commonly called direct bilirubin because it reacts directly in certain laboratory measuring methods.
Why is this test checked along with total bilirubin?
The two results help show whether an elevated bilirubin level is mainly due to increased unconjugated bilirubin or increased conjugated bilirubin, which can point toward different causes.
Does an abnormal result always mean there is serious liver disease?
No. An abnormal result can have several causes, including medications or temporary changes in liver function. Your clinician will interpret it using your medical history and other laboratory results.
  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