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Serum/plasma concentration of free bilirubin

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

This test measures the amount of bilirubin that is not bound to proteins in your blood, which can help assess liver function and detect conditions like jaundice or bile duct blockages.

Quick summary

["Free bilirubin levels help diagnose and monitor liver and bile-related issues."]

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

Key facts at a glance

LOINC
53010-5
Short code
SRP Ab SerPl Ql IF
Synonyms
SRP Ab SerPl Ql IF
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
if
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

Why Is This Test Done?

Your healthcare provider may order this test if you have symptoms like yellowing of the skin or eyes (jaundice), unexplained fatigue, or if they suspect liver disease, bile duct problems, or hemolysis (red blood cell destruction). It can also be part of routine liver function tests or when evaluating conditions like hepatitis or gallstones.

How Is the Test Performed?

A blood sample is taken from a vein, usually in your arm. The blood is then processed to separate the serum or plasma, where the bilirubin is measured using a specialized laboratory technique.

What Are Common Results and Their Meanings?

Higher-than-normal free bilirubin levels may indicate liver disease, bile duct obstruction, or red blood cell breakdown. Lower-than-normal levels are less commonly significant but could suggest certain genetic conditions or liver dysfunction.

What Can Affect This Test?

Factors that may influence results include liver disease, bile duct issues, hemolytic anemia, certain medications (like some antibiotics or anticonvulsants), and dehydration. Recent blood transfusions or certain foods (like large amounts of red meat or cruciferous vegetables) can also temporarily affect bilirubin levels.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Free bilirubin is a critical marker for diagnosing and monitoring liver and biliary system disorders. Elevated levels often signal conditions such as obstructive jaundice, liver cirrhosis, or hemolytic anemia. Monitoring free bilirubin helps guide treatment decisions and assess disease progression.

Short name

Free bilirubin

Frequently asked questions

What does a high free bilirubin level mean?
A high free bilirubin level often suggests a problem with your liver, bile ducts, or red blood cells. It may indicate conditions like jaundice, gallstones, liver disease, or hemolysis. Your doctor will review your symptoms and other test results to determine the cause and next steps.
Can diet affect my bilirubin test results?
Yes, certain foods and medications can temporarily influence bilirubin levels. Large amounts of red meat or cruciferous vegetables (like broccoli or Brussels sprouts) may affect results, as can some medications. Your doctor may advise you to avoid these if they suspect dietary interference.
Is this test painful?
The blood draw itself may cause a slight pinch or discomfort, but it is usually brief. Most people experience minimal pain afterward. If you have a hard time with needles, let your healthcare provider know so they can prepare accordingly.
  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