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Hepatitis B Surface Antigen (HBsAg), Serum — Qualitative

Published: August 9, 2026Updated: August 17, 2026

A qualitative blood test that checks for hepatitis B surface antigen, a marker of current or recent hepatitis B infection.

Quick summary

["A positive HBsAg result can indicate that you have a current or recent hepatitis B infection."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
21324-9
Short code
Deprecated H sativum IgE RAST Ql
Synonyms
Deprecated H sativum IgE RAST Ql
Category
liver
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
10
Ref high
40
Critical range
— – 500 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84484
SNOMED
302774002
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?

The hepatitis B surface antigen (HBsAg) test looks for a protein found on the surface of the hepatitis B virus. A positive result suggests the virus is present in your blood, which may represent an acute or chronic infection.

Why might I need this test?

This test may be used to screen for hepatitis B, investigate symptoms such as fatigue, nausea, abdominal discomfort, or jaundice, and help assess exposure risk. It is also commonly included in routine prenatal testing.

How is the test performed?

A blood sample is tested using an immunoassay, which detects the presence or absence of HBsAg. The result is reported as positive, negative, or occasionally as indeterminate and may be confirmed with additional testing.

How do I prepare for the test?

No special preparation is usually needed. Tell your healthcare professional if you have recently received hepatitis B treatment or a vaccine, because these can affect related test results.

Reference range

Adult: 10-40 U/LN/A

Specimen: serum

No special preparation required. Avoid fatty meals before the test if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Hepatitis B Surface Antigen (HBsAg)

Frequently asked questions

Does a positive HBsAg result mean I am immune to hepatitis B?
No. This test detects a marker of possible infection, not immunity. Immunity is generally assessed with a separate hepatitis B surface antibody test.
Can I still spread hepatitis B if this test is positive?
Yes. If the result reflects a current infection, the virus may be present in your blood and may be transmitted to others. Your healthcare professional can advise on precautions and treatment.
What happens if the HBsAg test is negative?
A negative result means hepatitis B surface antigen was not detected. Your clinician may consider other hepatitis B tests, such as hepatitis B surface antibody and hepatitis B core antibody, based on your situation.
  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 17, 2026. · Read our editorial policy