Getting tested for herpes typically involves either 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 reliable option. If you have no symptoms but want to know your status, a blood test can detect past infection, though it comes with some important limitations.
Swab Tests for Active Outbreaks
If you have a blister, sore, or anything that looks like it could be herpes, a healthcare provider can take a sample directly from the lesion using a swab. This is quick and straightforward: the provider breaks open or swabs the surface of a blister that hasn’t yet crusted over or started healing, then sends the sample to a lab. It can feel uncomfortable for a moment, especially if the sore is tender, but the process takes only seconds.
The lab typically uses a method called PCR (polymerase chain reaction), which detects the virus’s genetic material in the sample. PCR is highly sensitive and can distinguish between the two types of herpes: HSV-1 (which more commonly causes oral herpes) and HSV-2 (which more commonly causes genital herpes). Viral culture, an older method where the lab tries to grow the virus from the sample, is less commonly used now because PCR is faster and more accurate.
Timing matters with swab tests. The best window is during the first 48 hours of an outbreak, when the sore is fresh and fluid-filled. Once a sore starts scabbing over, the amount of detectable virus drops significantly, and the test becomes less reliable. If you notice a new sore, getting to a provider quickly improves your chances of an accurate result.
Blood Tests When No Symptoms Are Present
Blood tests don’t detect the virus itself. Instead, they look for antibodies your immune system produces in response to a herpes infection. The most useful type is an IgG antibody test, which indicates whether you’ve been infected at some point in the past. These tests use a protein called glycoprotein G to distinguish between HSV-1 and HSV-2, so your results will tell you which type (or both) you carry.
Your body needs time to build detectable antibodies after a new infection. Most experts recommend waiting at least 12 weeks after a possible exposure before getting a blood test. Testing too early can produce a false negative because your immune system hasn’t generated enough antibodies yet. If you test negative within the first few weeks after exposure, that result may not be meaningful.
One significant drawback of blood tests is that they cannot tell you where on your body the infection is. About 48% of the U.S. population carries HSV-1, and a positive HSV-1 blood test could mean you have oral herpes (cold sores), genital herpes, or an infection you’ve never noticed at all. This ambiguity is one reason routine screening isn’t standard practice.
Why Doctors Don’t Routinely Screen for Herpes
If you’ve ever wondered why herpes isn’t included in a standard STI panel, there’s a specific reason. The U.S. Preventive Services Task Force actively recommends against routine blood screening for herpes in people without symptoms. Their reasoning comes down to a few practical problems.
First, the widely available IgG blood tests have a meaningful rate of false positives, particularly when results fall in the low-positive range near the test’s cutoff value. In a large population of people without symptoms, these false positives add up quickly, meaning many people would receive an incorrect diagnosis. Second, the most reliable confirmatory test, called a Western blot, isn’t widely available, so it’s difficult to resolve ambiguous results at scale. Third, for someone with no symptoms and no outbreaks, the benefit of knowing their antibody status is unclear, since it’s uncertain whether treatment would be warranted. The task force concluded that the emotional and social harm of a false-positive diagnosis, along with unnecessary treatment, likely outweighs the benefits of screening everyone.
This doesn’t mean you can’t request a blood test. It means your provider may not offer one unless you ask, and they may want to discuss the limitations before ordering it.
What to Do With Low-Positive Results
If your IgG blood test comes back positive but the index value is low (close to the cutoff), your provider should recommend confirmatory testing. The FDA has specifically warned that low-positive results on HSV-2 blood tests carry a higher chance of being false. Options for confirmation include a supplemental test from a different manufacturer or, for the most definitive answer, a Western blot.
The Western blot for herpes is considered the gold standard, but it’s only performed at the University of Washington’s clinical virology lab in Renton, Washington. Your provider would need to draw a blood sample and ship it there on dry ice or cold packs, following specific handling instructions. The lab runs the test on Mondays and Thursdays. While this sounds involved, it can be worth pursuing if your initial result was ambiguous and you need a definitive answer. Your doctor can contact the lab directly for ordering instructions.
Where to Get Tested and What It Costs
You can get herpes testing at your primary care doctor’s office, a community health clinic, your local health department, or a Planned Parenthood location. Some people also use direct-to-consumer lab services that let you order blood work online and visit a local draw site without a doctor’s visit.
Cost varies depending on whether you have insurance, which tests you need, and where you go. STI testing generally ranges from $0 to $250 out of pocket. Many Planned Parenthood centers and community clinics offer free or reduced-cost testing based on income, and government programs can cover the cost for people who qualify. If you have health insurance, STI testing is often covered with little to no copay, especially if your provider orders it as part of a medical evaluation for symptoms.
Which Test to Choose
The decision is relatively simple. If you have an active sore or blister right now, get a swab test as soon as possible. Don’t wait for it to heal. Call your provider the same day you notice a new lesion, because the accuracy of swab testing drops as sores begin to crust over.
If you have no symptoms but want to know whether you carry HSV-2 (the type most associated with genital herpes), request an IgG blood test. Make sure at least 12 weeks have passed since any potential exposure. Be prepared for the possibility of an ambiguous result that requires follow-up.
If you’re concerned about HSV-1 specifically, keep in mind that a positive result won’t tell you whether the infection is oral or genital. Given how common HSV-1 is in the general population, a positive result may simply confirm something like a history of cold sores in childhood. For most people without symptoms, HSV-1 blood testing provides limited actionable information.