HBsAg (Hepatitis B Surface Antigen)
What Is This Test?
The HBsAg (Hepatitis B Surface Antigen) test is a blood test used to detect the presence of the Hepatitis B virus (HBV) in the body. It identifies a protein (surface antigen) found on the outer surface of the virus. If HBsAg is detected in the blood, it usually indicates an active Hepatitis B infection, which may be acute (recent) or chronic (long-term).
This test is commonly used for screening, diagnosis, blood donor screening, prenatal testing, and monitoring individuals at risk of Hepatitis B infection.
Why this test is performed?
Doctors may recommend the HBsAg test to:
- Screen for Hepatitis B infection
- Diagnose acute or chronic Hepatitis B
- Evaluate abnormal liver function test (LFT) results
- Screen pregnant women during pregnancy
- Screen blood and organ donors
- Test healthcare workers after exposure to blood or body fluids
- Screen before surgery or certain medical procedures
- Check before starting chemotherapy or immunosuppressive therapy
- Evaluate individuals with a family history of Hepatitis B
Monitor people at high risk of HBV infection
Test Preparation
- No special preparation is usually required.
- You can eat and drink normally unless your doctor advises otherwise.
- Inform your healthcare provider about any medications or recent vaccinations.
- Tell the laboratory if you have recently received blood products or undergone dialysis.
Medical disclaimer
This article is for general information and education only. It is not medical advice, does not create a doctor–patient relationship, and is not a substitute for consultation with a qualified doctor who has assessed your individual situation. Never delay seeking medical advice because of something you have read here.
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