For hepatitis A and hepatitis B serology, which antibodies are IgM and which are IgG?

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Last updated: September 29, 2026 • View editorial policy

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Hepatitis A and B Antibody Types

For hepatitis A, IgM indicates acute infection while IgG indicates past infection or immunity; for hepatitis B, IgM anti-HBc indicates acute infection while IgG anti-HBc (detected as "total anti-HBc" after IgM wanes) indicates past or chronic infection. 1

Hepatitis A Serology

IgM anti-HAV:

  • Appears during acute hepatitis A infection
  • Confirms diagnosis of acute HAV infection
  • Detectable by 4-6 weeks after exposure
  • Persists for 2-4 months (up to 62 days documented) 1, 2

IgG anti-HAV:

  • Indicates past infection or immunity from vaccination
  • Appears after IgM and persists for life
  • Detectable by 4 weeks after clinical presentation 1

Important caveat: Anti-HAV total antibody tests (detecting both IgM and IgG combined) can be positive in asymptomatic patients with normal liver tests, indicating resolved infection rather than acute disease. The presence of IgM specifically is required to diagnose acute infection 1.

Hepatitis B Serology

IgM anti-HBc (antibody to hepatitis B core antigen):

  • Appears 1-2 weeks after HBsAg in acute infection
  • Diagnostic of acute or recently acquired HBV infection
  • Remains detectable for approximately 6 months
  • The only marker present during the "window period" (when HBsAg has disappeared but anti-HBs hasn't appeared yet) 3, 1
  • Can persist at low levels during chronic infection exacerbations, but typically not detectable by standard U.S. assays 4

IgG anti-HBc (detected as "total anti-HBc"):

  • Appears at onset of symptoms in acute infection
  • Persists for life in the majority of persons
  • After IgM becomes undetectable (within 6 months), IgG anti-HBc predominates 3
  • Indicates past infection when present with anti-HBs
  • Indicates chronic infection when present with HBsAg (without IgM) 3, 1, 5

Critical distinction: There is no commercially available test specifically for HBc IgG antibody in the U.S. 1. Instead, "total anti-HBc" tests detect both IgM and IgG together. When IgM anti-HBc is negative but total anti-HBc is positive, this indicates the IgG component is present, signifying past or chronic (not acute) infection.

Clinical Algorithm for Interpretation

For suspected acute hepatitis:

  • Order IgM anti-HAV for hepatitis A
  • Order IgM anti-HBc (not just total anti-HBc) for hepatitis B
  • Both IgM tests confirm acute infection of their respective viruses 1, 5

For immunity screening:

  • Order IgG anti-HAV or total anti-HAV for hepatitis A immunity
  • Order anti-HBs for hepatitis B immunity (from infection or vaccination)
  • Total anti-HBc indicates past HBV infection specifically (not vaccination) 3, 6

Common pitfall: Ordering only "total anti-HBc" without IgM anti-HBc in suspected acute hepatitis B will miss the diagnosis, as total anti-HBc can be positive in both acute and chronic infection 4.

References

5
Guideline

sexually transmitted infections treatment guidelines, 2021.

MMWR Recommendations and Reports, 2021

6
Guideline

kasl clinical practice guidelines: management of chronic hepatitis b.

Clinical and Molecular Hepatology, 2016

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This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.