HepatologyGastroenterology

HBsAg (Australia Antigen)

Normal Range
Negative (Non-reactive)
Sample Type
Serum
Fasting
No
Unit
Index

Function

The Hepatitis B Surface Antigen (HBsAg), historically known as the Australia Antigen, is the earliest serum marker for an active Hepatitis B Virus (HBV) infection. Its presence indicates that the virus is replicating and that the individual is infectious to others.

Why it is Ordered

HBsAg is the cornerstone of HBV screening. It is ordered for:

  • General Screening: In populations at high risk for HBV.
  • Prenatal Care: Routine screening for all pregnant women to prevent mother-to-child transmission.
  • Blood Donation: To ensure the safety of the blood supply.
  • Symptom Evaluation: For patients showing signs of hepatitis, such as jaundice, dark urine, and fatigue.

Associated Conditions

  • Acute Hepatitis B: The initial short-term infection phase.
  • Chronic Hepatitis B: Defined by the persistence of HBsAg for more than six months, increasing the risk of cirrhosis and hepatocellular carcinoma (liver cancer).
  • Fulminant Hepatitis: A rare but life-threatening rapid liver failure.

Early detection through HBsAg allows for antiviral intervention and lifestyle modifications to prevent liver damage and viral spread.

Check Your Result

Check Your Result

Interactive
Index

Enter your lab result to see where you stand compared to the standard reference range.

Why Context Matters

HBsAg results can occasionally yield false positives shortly after receiving a Hepatitis B vaccine (usually within 1-2 weeks). Furthermore, 'occult' Hepatitis B can exist where HBsAg is negative but viral DNA is present. Confirmation with HBsAb (surface antibody) and HBcAb (core antibody) is necessary for a complete clinical picture.

Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.

Clinical References

Source-of-truth databases and clinical guidelines for HBsAg (Australia Antigen):

Research & Guidelines

Related Indicators

Bile Salts & Pigments - Urine

View Range

Bile Salts

View Range

Bile Pigments (Urinary Bilirubin)

View Range
DR

Medically Reviewed by Dr. Binoy Babu, MBBS

Board Certified Doctor • 10+ Years Clinical Experience

Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.

Get Notified When Dr. Babu Is Available