Herpes can be tested two main ways: a swab of an active sore or a blood test that checks for antibodies. Which test you need depends on whether you currently have symptoms. If you have visible blisters or sores, a swab test is the most direct route. If you have no symptoms but want to know your status, a blood test can detect past infection, though it takes 2 to 12 weeks after exposure for antibodies to develop enough to be detected.
Swab Tests for Active Sores
When you have a blister, sore, or anything that looks like an outbreak, a healthcare provider can swab fluid directly from the lesion. That sample is then analyzed one of two ways: viral culture or PCR testing.
Viral culture grows the virus from your sample in a lab. It’s highly specific, meaning a positive result is reliable, but it misses infections roughly half the time. It also takes a while. In one study comparing the two methods, culture results took a median of 7.6 days to come back.
PCR testing looks for the virus’s genetic material in the sample. It’s significantly more sensitive, catching infections that culture misses. In the same study, PCR identified the virus in 85.7% of confirmed cases compared to just 42.9% for culture, and results came back in less than a day (median 0.8 days). PCR produced zero false positives. For these reasons, PCR has largely become the preferred swab test in clinical settings.
The testing method is the same regardless of whether your sores are oral or genital. A provider swabs the affected area, and the lab can determine whether the virus is HSV-1 or HSV-2, which matters for understanding your risk of future outbreaks and transmission.
Blood Tests When There Are No Symptoms
If you don’t have active sores, the only option is a blood test that detects antibodies your immune system has made in response to the virus. These are called type-specific IgG tests, and they can distinguish between HSV-1 and HSV-2. An older type of blood test (IgM) is not recommended because it can’t reliably tell the two types apart and often gives misleading results.
Timing matters. Your body needs 2 to 12 weeks after infection to produce enough antibodies for a blood test to detect them. Testing too early in that window can produce a false negative. If you had a specific exposure you’re concerned about, waiting at least 12 weeks gives you the most reliable result.
The False Positive Problem
The most widely used screening blood test can produce false positives, particularly when the result falls in a low-positive range. Specifically, index values between 1.10 and 3.50 on this test have a high rate of being falsely positive. The CDC recommends that any result in that range be confirmed with a second, more accurate test before you consider the diagnosis settled.
The gold standard confirmatory test is the HSV Western Blot, developed at the University of Washington. It requires a blood draw, and the sample must be shipped frozen to their lab in Seattle. It’s not available at most standard clinics, so you may need to ask your provider to order it specifically or contact the University of Washington’s Clinical Virology Lab directly. If your screening blood test came back with a low-positive number and you’re unsure whether to trust it, this is the test that gives a definitive answer.
Who Should Get Tested
The CDC does not recommend routine herpes blood testing for the general population, including asymptomatic pregnant women. The reasoning isn’t that herpes is unimportant. It’s that the available screening blood tests produce enough false positives in low-risk people to cause more confusion than clarity.
Blood testing is recommended or worth considering in specific situations:
- Recurring genital symptoms that haven’t been confirmed by a swab test
- A partner who has genital herpes and you want to know if you already carry the virus
- A previous clinical diagnosis of genital herpes that was never lab-confirmed
- Higher-risk profiles, such as people with 10 or more lifetime sexual partners, people being evaluated for other STIs, or people living with HIV
If you fall into one of these categories, a type-specific IgG blood test is a reasonable step. Just keep the index value issue in mind and ask for confirmatory testing if your result lands in that 1.10 to 3.50 zone.
At-Home Test Kits
Several companies now sell mail-in herpes test kits that let you collect a blood sample at home and send it to a lab. These can be appealing for privacy and convenience, especially if getting to a clinic is difficult or if the stigma around testing feels like a barrier.
The trade-off is reliability. Accuracy depends heavily on how well you collect the sample, and poor collection is common outside a clinical setting. There’s also less oversight of some mail-order labs compared to hospital-affiliated ones. A false negative from a home kit could give you false reassurance, while a false positive (particularly in that low-positive range) could cause unnecessary alarm without a provider there to explain context or order confirmatory testing.
If you use an at-home kit and get a positive result, treat it as a starting point, not a final answer. A clinical lab can re-run the test or order the Western Blot to confirm.
Testing During Pregnancy
Routine herpes blood screening is not recommended for pregnant women without symptoms. However, type-specific blood tests can be useful in certain pregnancy scenarios, particularly for identifying women who don’t have herpes but whose partners do. A first-time herpes outbreak near delivery carries a significant risk to the newborn, so knowing your status relative to your partner’s can guide important decisions in the third trimester.
Routine swab cultures during late pregnancy are also not recommended for women with a known history of recurrent genital herpes. The standard approach is clinical monitoring for active lesions as the due date approaches, not repeated lab testing.
Where to Get Tested
Your primary care provider, an OB-GYN, a sexual health clinic, or a Planned Parenthood location can all order herpes testing. If you have active sores, walk-in urgent care clinics can usually perform a swab. For blood testing, any lab that processes standard STI panels can run a type-specific IgG test.
For the Western Blot confirmatory test, you’ll likely need to work with your provider to send a sample to the University of Washington lab, as it’s the only facility that runs it. The lab accepts samples from outside providers with specific shipping requirements (frozen, shipped on dry ice, arriving within a set timeframe).