Antibody tests check your blood by looking for antibodies, which may tell you if you had a past infection with the virus that causes COVID-19. Antibodies are proteins that help fight off infections and can provide protection against getting that disease again (immunity). Antibodies are disease specific.
Antibody tests should not be used to diagnose a current COVID-19 infection, except in instances in which viral testing is delayed. An antibody test may not show if you have a current COVID-19 infection because it can take 1–3 weeks after infection for your body to make antibodies.