Window periods

Different authorities give slightly different estimates for the duration of the window period between exposure and the ability of third-generation tests to detect infection:

  • Between three weeks (21 days) and six weeks (42 days)1
  • Between two and eight weeks, with an average of 25 days; 97% of people develop antibodies within three months2
  • 20-25 days3
  • 22 days4
  • One month5

Second-generation ELISAs were estimated to detect infection after 42 days and first-generation after 63 days.4

Related Links


  1. Branson BM State of the art for diagnosis of HIV infection. Clin Infect Dis 45:S221-225, 2007
  2. Coombs RW Clinical laboratory diagnosis of HIV-1 and use of viral RNA to monitor infection. In Holmes KK (editor), Sexually Transmitted Diseases. New York: McGraw-Hill, 2008
  3. Maldarelli F Diagnosis of Human Immunodeficiency Virus infection. In Mandell, Douglas and Bennett’s Principles and Practice of Infectious Diseases (sixth edition). Philadelphia: Elsevier Churchill Livingstone, 2004
  4. Parry JV et al. Towards error-free HIV diagnosis: guidelines on laboratory practice. Comm Dis Pub Health 6:334-350, 2003
This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.
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