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Direct Bilirubin, Serum/Plasma — Mass Concentration

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

Direct bilirubin measures the fraction of bilirubin that reacts directly in the laboratory assay, primarily conjugated bilirubin, using a serum or plasma sample.

Quick summary

["This blood test helps evaluate the conjugated bilirubin portion of total bilirubin and is usually interpreted with other liver tests."]

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

Key facts at a glance

LOINC
109066-1
Short code
Bilirub Indirect Msmt SerPl
Synonyms
Bilirub Indirect Msmt 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?

Direct bilirubin is the part of bilirubin that reacts directly with the laboratory reagent. It mainly represents bilirubin that has been processed by the liver, also called conjugated bilirubin.

Why might I need this test?

This test may be ordered to help evaluate liver function or jaundice. It is often reviewed with total bilirubin and other tests, such as alkaline phosphatase and liver enzymes.

How is the test performed?

A blood sample is collected, and the serum or plasma portion is analyzed in the laboratory to measure direct-reacting bilirubin. The sample is usually obtained through a routine blood draw.

How do I prepare for the test?

Fasting is generally not required for this test unless your healthcare professional gives different instructions. Tell the laboratory if you have recently received a blood transfusion or if the sample may be affected by unusual bruising or excessive hemolysis.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Direct Bilirubin

Frequently asked questions

How is direct bilirubin different from total bilirubin?
Total bilirubin includes both directly reacting and indirectly reacting bilirubin. Direct bilirubin represents the fraction that reacts directly in the assay and primarily reflects conjugated bilirubin.
Does a high direct bilirubin result confirm a particular liver disease?
No. It can occur with several conditions involving the liver or bile ducts, so your healthcare professional will interpret it with your other test results and medical history.
Do I need to fast before this test?
Usually not, unless your healthcare professional specifically requests fasting. Follow the instructions provided with your laboratory order.
  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