Herpes tests: which one, when, and what the result means

The two kinds of test

A swab test looks for the virus in a sore. A blood test looks for antibodies, the proteins your body makes after it meets the virus. They answer different questions. A swab can tell you what is causing this sore, and a blood test can tell you whether you carry the virus at all, even with no sores.

When CDC says to test, and when it says not to

The CDC's testing page starts here: CDC recommends herpes testing for people with genital symptoms. Blisters or sores on or around the genitals count. If that is you, book a clinic visit.

The same page explains why it does not test everyone: CDC does not recommend herpes testing for people without symptoms in most situations. This is because of the limits of a herpes blood test and the possibility of a wrong test result. The chances of wrong test results are higher for people who are at low risk of infection. That last sentence matters most if you have no symptoms and no known exposure. If you are low risk, a positive result deserves a second look. You can still ask for a blood test. Just go in knowing what a result can and can't tell you.

Why a swab works best on a fresh sore

If you have a sore, the CDC says a provider They can also take a sample or swab from a blister or sore that is not already crusted over or healing. In fact, the tests that use these samples work best. So go while the blister is new, before it scabs.

Waiting costs you accuracy. From the treatment guidelines: The sensitivity of viral culture is low, especially for recurrent lesions, and decreases rapidly as lesions begin to heal A negative swab from a healing sore doesn't rule herpes out. If that happens, ask whether a blood test or a second swab at the next outbreak makes sense.

Blood tests: ask for type-specific, and know the limits

Not every herpes blood test tells the two types apart: Type-common antibody tests do not distinguish between HSV-1 and HSV-2 infection; therefore, type-specific serologic assays should be requested A type-common result that just says "herpes" can't tell you whether you carry HSV-1 or HSV-2. That gap matters. The WHO says Type 1 (HSV-1) mostly spreads by oral contact and causes infections in or around the mouth (oral herpes or cold sores). It can also cause genital herpes. Most adults are infected with HSV-1. So ask for the type-specific test by name.

Even the right test has limits. The guidelines put the sensitivity of type-specific HSV-2 tests at 80% to 98%, and add that false-negative results might be more frequent at early stages of infection The bigger problem runs the other way. For the most commonly used test, the CDC warns that results at low index values of 1.1 to 3.0 are often falsely positive. One study the CDC cites put that test's overall specificity at 57.4%, and at 39.8% for results in that low band.

A clearly positive HSV-2 result is an answer. A low-positive one often isn't. If your index value sits in that band, ask your clinician about a confirmatory test before you treat it as a diagnosis.

How long after exposure to test

Antibodies need time. Both type-specific and type-common antibodies to HSV develop during the first weeks after infection and persist indefinitely, per the CDC's guidelines. The CDC's testing page gives the outer limit: After exposure, it can take up to 16 weeks or more for current tests to detect infection. A blood test a week after a worrying night can come back negative even if you were infected.

For a recent suspected HSV-2 exposure, the guidelines add that in cases of recent suspected HSV-2 acquisition, repeat type-specific antibody testing 12 weeks after the presumed time of acquisition is indicated. The guide to testing after exposure walks through that timing, what to do if symptoms appear in the meantime, and how to read the result.

"Tested for everything" may not include herpes

A full STI panel may leave herpes out. The CDC says so directly: Herpes blood tests may or may not be part of the tests your healthcare provider gives you. Its advice is simple: Ask them which infections they are and are not testing you for and why.

This matters in both directions. If a new partner says they tested clean, that may not cover herpes. If you are the one saying it, check what your panel actually was before you repeat it.

What the result means for dating

A positive result starts with one question: which type? According to the CDC, Recurrences and subclinical shedding are much more frequent for HSV-2 genital herpes infection than for HSV-1 genital herpes. That changes what you tell a partner, and the HSV-1 vs HSV-2 guide covers the details.

A negative result is good news about that test, on that day. Given the limits above, don't treat it as a guarantee to a partner. Tell them what test you had and when, and let them weigh it.

If the result is positive and clear, the next steps are the same as for anyone newly diagnosed. The dating after diagnosis guide covers the first weeks, and the first disclosure guide covers what to say and when. You can't control how a partner reacts. You can go into the conversation knowing exactly what your test does and doesn't show.