CDC recommends herpes testing for people with genital symptoms. If you have a fresh genital sore or blister, a clinician can swab it and test the sample for herpes simplex virus. A swab-based NAAT, including PCR, is usually the most useful test when a lesion is present. CDC does not recommend herpes testing for people without symptoms in most situations. A blood test answers a different question and has more limits, especially when the exposure was recent.

What happens at a herpes test appointment?

A clinician will ask about your symptoms and sexual and medical history. If there is a sore, blister, or other lesion, they may swab it. The sample can be tested for HSV with a NAAT/PCR test; in some settings, a viral culture is used.

CDC describes HSV NAAT tests as the most sensitive tests for genital lesions. Viral culture can miss more infections, especially when a lesion is healing or has come back before. A positive lesion test can also be typed to show whether HSV-1 or HSV-2 was detected.

If there is no lesion to swab, the clinician may discuss a type-specific blood test. That test looks for antibodies, rather than the virus in a sore. It may be considered in situations such as recurring or unusual symptoms after a negative lesion test, a clinical diagnosis that was never confirmed in a lab, or a partner who has genital herpes.

Why timing changes the answer

A blood test can be negative early in an infection because the body may not have made enough detectable antibodies yet. When recent HSV-2 acquisition is suspected, the CDC 2021 guidelines say to repeat type-specific antibody testing 12 weeks after the presumed acquisition.

A blood test can also be wrong in the other direction. Low-positive HSV-2 results from some enzyme immunoassays can be falsely positive. The CDC recommends confirming a low-positive result with a different method before interpreting it. Ask which assay was used and whether a confirmatory test is available.

A common misconception

A blood test is not a complete record of when herpes began or who transmitted it. CDC says a blood test cannot answer those questions. Your clinician interprets the result alongside symptoms, sample type, and timing.

Do not use an HSV IgM test to sort this out. CDC says IgM is not type specific and can be positive during recurrent oral or genital episodes, so it is not useful for diagnosing a new infection.

What a test cannot tell you by itself

A result does not tell you exactly when an infection began or who transmitted it. Your clinician needs the result, the sample type, your symptoms, and the test’s limitations together. Blood PCR is not the routine test for genital herpes; CDC reserves it for concern about disseminated infection.

If you have a new lesion or other symptoms, contact a healthcare professional. Do not wait for an online test explanation to replace an exam.

Questions to take to your clinician

  • Is a lesion present that can be swabbed today?
  • Is the test a NAAT/PCR, viral culture, or type-specific antibody test?
  • If this is a blood test, could the timing make a negative result too early?
  • If the result is low positive, what confirmatory method will be used?
  • What other causes of the sore should be checked?

Sources and update note

This guide was checked on September 27, 2026. It uses the CDC’s Screening for Genital Herpes page and the Herpes STI Treatment Guidelines. Medical guidance can change, so use the linked CDC pages and your clinician’s advice for current decisions.

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