Getting tested for herpes (HSV) depends on whether you have visible symptoms. If you have sores or blisters, a swab test taken directly from the lesion is the most accurate option. If you don’t have symptoms, a blood test that looks for antibodies is the main route, though these tests come with important limitations you should understand before ordering one.
Swab Tests: The Best Option During an Outbreak
If you have an active sore, blister, or ulcer, a healthcare provider can swab the lesion and send the sample to a lab. There are two types of swab tests: viral culture and PCR (polymerase chain reaction). PCR is the preferred method because it’s significantly more sensitive. In head-to-head comparisons, PCR detects the virus 100% of the time when it’s present, while culture catches it only about 50% of the time. Both tests are 100% specific, meaning a positive result on either one is reliable.
Timing matters. Swab tests work best on fresh lesions, ideally within the first 48 hours of a sore appearing. As lesions begin to heal and crust over, the amount of virus on the surface drops, and the test becomes less likely to pick it up. A swab test also tells you whether you have HSV-1 or HSV-2, which is useful for understanding your infection and its likely recurrence pattern.
Blood Tests: What They Measure and When They Work
Blood tests don’t detect the virus itself. They detect antibodies your immune system produces in response to infection. The test you want is called an IgG test, which looks for long-term antibodies specific to either HSV-1 or HSV-2. These antibodies take time to develop after exposure. The CDC notes it can take up to 16 weeks or more for current tests to detect infection, so testing too early after a possible exposure can produce a false negative.
If you were potentially exposed recently and your blood test comes back negative, you may need to retest after the window period has passed to get a reliable result.
Why IgM Tests Are Unreliable
Some providers still order IgM blood tests for herpes, but major health organizations advise against them. IgM tests can’t accurately distinguish between HSV-1 and HSV-2. They also cross-react with other viruses in the same family, like the virus that causes chickenpox or the one that causes mono, leading to misleading positive results.
There’s another common misconception: many people assume a positive IgM result means the infection is new. That’s not the case. IgM antibodies show up during recurrent outbreaks in about a third of people who’ve been infected for years. At the same time, IgM tests miss up to half of genuinely new infections confirmed by swab. If your provider orders an IgM test, it’s reasonable to ask for an IgG test instead.
Interpreting a Positive Blood Test
Not all positive IgG results are equally trustworthy. The most widely used screening test, the HerpeSelect HSV-2 IgG assay, reports results as an index value. A value below 0.90 is negative and above 1.10 is considered positive. But values in the low-positive range of 1.10 to 3.50 have a high rate of false positives.
The CDC recommends that anyone with an index value in that 1.10 to 3.50 range get a confirmatory test before accepting the diagnosis. The gold standard confirmatory test is the Western Blot, offered through the University of Washington Clinical Virology Lab. It’s not FDA-cleared but is considered the most accurate herpes blood test available. You or your provider can contact the lab directly at 206-685-8037 for ordering instructions. The test requires a standard blood draw, and results are reported for both HSV-1 and HSV-2.
If your index value is above 3.50, the result is much more likely to be a true positive, and confirmatory testing is generally not necessary.
Why Routine Screening Isn’t Recommended
You might be surprised to learn that neither the CDC nor the U.S. Preventive Services Task Force recommends routine herpes blood testing for people without symptoms. This isn’t because herpes isn’t common. It’s because the available blood tests produce too many false positives when used on people with no reason to suspect infection.
The USPSTF estimated that in a group of 10,000 people with a typical HSV-2 prevalence of 15%, screening would produce about 1,585 true positives alongside 1,445 false positives. That’s nearly a coin flip for any individual who tests positive, which can cause significant anxiety and relationship disruption over a diagnosis that may not be real. For people without symptoms, there’s also no clear benefit to antiviral treatment, making the screening less actionable even when results are accurate.
This doesn’t mean you can’t request a test. It means that if you do, go in understanding the limitations and be prepared to follow up with confirmatory testing if your result falls in the low-positive range.
Where to Get Tested
You have several options depending on your situation and budget. A primary care doctor, gynecologist, or urologist can order either a swab or blood test. Planned Parenthood and local sexual health clinics offer testing on a sliding scale based on income, and some visits may be free. STD testing generally costs anywhere from $0 to $250 out of pocket depending on how many infections you’re being tested for and where you go. Many insurance plans cover STD testing as preventive care with no copay.
At-home test kits are also available and increasingly popular. These typically involve a finger-prick blood sample you mail to a lab. They can be useful for getting a reliable negative result, but positive results on at-home herpes tests carry the same false-positive concerns as any other IgG blood test. If you test positive through a home kit, plan on getting additional testing through a provider to confirm.
Choosing the Right Test for Your Situation
If you have active sores, get a PCR swab as soon as possible. This gives you the most accurate result and tells you which type of HSV you have. Don’t wait for the sores to start healing.
If you don’t have symptoms but want to know your status, request an HSV-1 and HSV-2 IgG blood test. Make sure at least 16 weeks have passed since any potential exposure. Ask your provider specifically for an IgG test, not IgM. If your HSV-2 IgG index value comes back between 1.10 and 3.50, request the University of Washington Western Blot before drawing any conclusions.
If you’ve never had symptoms and your partner has herpes, a type-specific IgG blood test can help determine whether you already carry the same type. Many people with HSV-1 or HSV-2 never develop noticeable symptoms, so a blood test is the only way to know for sure outside of an outbreak.