How Long Does It Take for Herpes to Show up on a Blood Test?

Herpes blood tests can detect antibodies 12-16 weeks after initial infection, though some people develop detectable levels as early as 6 weeks. Type-specific IgG blood tests can distinguish HSV-1 antibodies from HSV-2 antibodies, but their accuracy varies. False-positive results can occur, especially with some low-positive HSV-2 results, so confirmatory testing may be recommended. A positive blood test also cannot show when the infection occurred or, for HSV-1, whether it is oral or genital. During the window period before antibodies develop, blood tests may show false negatives even when someone is infected. If sores or blisters are present, a clinician can swab them for a PCR or other nucleic acid amplification test, which can detect the virus directly and is generally preferred over blood testing for diagnosing an active lesion.