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Direct Bilirubin, Serum/Plasma — Mass Fraction

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

Measures the direct bilirubin fraction in blood, which is mainly used to help evaluate liver function and bile duct drainage.

Quick summary

["Direct bilirubin helps assess liver function and may rise with liver injury or impaired bile flow."]

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

Key facts at a glance

LOINC
35672-5
Short code
Bilirub Direct MFr SerPl
Synonyms
Bilirub Direct 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?

Bilirubin is a yellow pigment produced as the body breaks down old red blood cells. Direct bilirubin, also called conjugated bilirubin, is the portion that the liver has processed and is ready to excrete in bile.

Why might I need this test?

This test may be ordered as part of a liver panel or when symptoms suggest liver inflammation, impaired bile flow, or a bile duct blockage. It is often interpreted together with total bilirubin, indirect bilirubin, and other liver tests.

How is the test performed?

A blood sample is collected and analyzed in a laboratory to measure the direct bilirubin fraction. The sample may be serum or plasma, depending on the laboratory’s testing method.

How do I prepare for the test?

Fasting is usually not required for this test unless your clinician gives specific instructions. Tell the healthcare professional ordering the test about any medicines, pregnancy, or recent medical procedures that could affect the result.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Direct Bilirubin

Frequently asked questions

What is the difference between direct and total bilirubin?
Total bilirubin includes both direct and indirect forms, while direct bilirubin measures the fraction that has been processed by the liver. The results are often compared to help distinguish different causes of an elevated bilirubin level.
Does a high direct bilirubin result always mean the bile ducts are blocked?
No. A high result can have several causes, including liver inflammation or impaired bile production, and it does not by itself confirm a blockage. Your clinician will interpret it with the rest of your liver panel and your symptoms.
Is fasting required for a direct bilirubin blood test?
Usually not, but fasting or other preparation may be needed when the test is ordered as part of a larger panel. Follow any instructions provided by your clinician or laboratory.
  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