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Hepatitis B Detection Window: How Soon Can Blood Tests Identify Infection?

HBsAg (hepatitis B surface antigen) is the earliest marker, detectable in blood:

  • 1–2 weeks post-exposure (range: 1–9 weeks)
  • Precedes symptoms by 2–4 weeks
  • Peaks during acute illness; clears in ~90% of immunocompetent adults

Serologic Window Period

Testing Recommendations

  • Post-exposure: Baseline HBsAg, anti-HBc, anti-HBs; repeat at 6 weeks, 3 months, 6 months.
  • Screening: HBsAg + anti-HBc + anti-HBs (triple panel) distinguishes immune, susceptible, acute, chronic.
  • Early detection: HBV DNA PCR can detect infection ~1 week post-exposure; used in high-risk exposures or blood donor screening.

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MarkerAppearanceSignificance
HBsAg1–9 weeksActive infection (acute or chronic)
HBV DNA~1 weekViral replication; earliest direct measure
Anti-HBc IgM2–4 weeksAcute infection marker
Anti-HBsMonths (after clearance)Immunity (recovery or vaccine)