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Direct Bilirubin, Serum/Plasma — Substance Concentration

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

Direct bilirubin measures the fraction of bilirubin that has been processed by the liver. It is used along with other liver tests to help evaluate liver function and bile duct problems.

Quick summary

["Direct bilirubin is a liver-related blood test used to help evaluate liver function and the flow of bile."]

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

Key facts at a glance

LOINC
14629-0
Short code
Bilirub Direct SerPl-sCnc
Synonyms
Bilirub Direct 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?

Direct bilirubin, also called conjugated bilirubin, is the part of bilirubin that has been changed by the liver so it can be eliminated in bile. This test measures its concentration in a serum or plasma blood sample.

Why might I need this test?

Your clinician may order direct bilirubin as part of a liver panel or to help investigate jaundice, liver disease, gallbladder problems, or a possible blockage of the bile ducts. It is usually interpreted together with total bilirubin and other laboratory results.

How is the test performed?

A blood sample is collected from a vein and placed in a tube. The laboratory separates serum or plasma and measures direct bilirubin using an automated laboratory method. No special procedure is generally required for the blood draw itself.

How do I prepare for the test?

Fasting is not usually required for a direct bilirubin test, but follow your clinician's instructions. Tell the laboratory if you are pregnant or have had a blood transfusion recently, because these factors can affect bilirubin results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

An elevated direct bilirubin level may occur with liver inflammation or damage, impaired bile excretion, or a blockage of the bile ducts. A low direct bilirubin level is less commonly significant on its own. Results should be interpreted with total bilirubin, the rest of your liver tests, your symptoms, and your medical history.

Short name

Direct Bilirubin

Frequently asked questions

What does direct bilirubin measure?
It measures the fraction of bilirubin that the liver has processed and made ready for excretion in bile.
Why are direct and total bilirubin both reported?
Comparing them helps show whether an elevated bilirubin level is mainly from direct or indirect bilirubin. The results provide more context when evaluating jaundice or liver disease.
Do I need to fast for this test?
Fasting is usually not necessary, although your clinician may include it in a broader testing plan. Follow the specific instructions provided for your blood test.
  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