Getting tested for herpes depends on whether you have visible symptoms. If you have an active sore or blister, your doctor can swab it directly for the most accurate result. If you have no symptoms but want to know your status, a blood test can detect antibodies your immune system produces after infection. Each path has different accuracy, timing, and availability, and understanding the differences will help you get a result you can trust.
Swab Tests for Active Sores
If you have a blister, sore, or anything that looks like it could be a herpes outbreak, the best option is a swab test performed on the lesion itself. The preferred method is called nucleic acid amplification testing (NAAT), sometimes referred to as a PCR test. It detects the virus’s genetic material directly and is highly sensitive and specific.
Viral culture, the older approach, involves swabbing the sore and trying to grow the virus in a lab. It’s less sensitive than PCR, and its accuracy drops significantly as a lesion starts to heal or during recurrent outbreaks rather than a first episode. If you’re going to get a swab, timing matters: go as soon as possible after a sore appears, ideally while it’s still fresh and fluid-filled. A crusted-over or healing sore is much harder to test accurately.
Both swab methods can tell you whether you have HSV-1 or HSV-2, which is useful information since the two types behave differently over time.
Blood Tests When You Have No Symptoms
Blood tests don’t detect the virus itself. They look for IgG antibodies, proteins your immune system creates in response to herpes infection. This means a blood test can tell you whether you’ve been infected even if you’ve never noticed a symptom.
The catch is timing. After exposure, it can take up to 16 weeks or more for antibodies to reach detectable levels. If you test too early, you can get a negative result even though you’re infected. If you had a specific exposure you’re worried about, waiting at least 12 to 16 weeks gives the test its best chance of catching an infection.
The most widely used screening test is the HerpeSelect HSV-2 IgG enzyme immunoassay. It returns a numerical index value rather than a simple yes or no. A value below 0.90 is negative, 0.90 to 1.09 is equivocal, and 1.10 or above is considered positive. But there’s an important nuance: index values in the low-positive range of 1.10 to 3.50 have a high rate of false positives. The CDC recommends that any result in that range be confirmed with a second, more reliable test before you accept the diagnosis.
Why IgM Tests Should Be Avoided
Some providers still order an IgM blood test, which looks for a different, earlier-appearing antibody. This test is unreliable for herpes and is not recommended by major health organizations. IgM tests can’t accurately distinguish between HSV-1 and HSV-2. A person who only has HSV-1 (oral herpes, which the majority of adults carry) could easily receive a false positive result for HSV-2.
IgM antibodies also cross-react with related viruses like the one that causes chickenpox, producing misleading positives. And despite a common assumption, a positive IgM result does not reliably indicate a new infection. If a provider offers you an IgM test for herpes, ask for an IgG test instead.
Confirming a Low-Positive Result
If your IgG screening comes back in that uncertain 1.10 to 3.50 range, the gold standard confirmatory test is the herpes Western blot. This test is performed at the University of Washington’s Clinical Virology Lab in Renton, Washington, and it’s the most accurate blood test available for herpes. It requires a standard blood draw (a serum sample), and the lab runs results on Mondays and Thursdays.
The Western blot isn’t available at walk-in labs. Your doctor needs to contact the University of Washington Clinical Virology Lab directly at 206-685-8037 for ordering instructions. It’s a lab-developed test, not FDA-cleared, but it’s widely recognized as the definitive test when screening results are ambiguous. If you’ve received a low-positive result and want certainty before making decisions about disclosure or treatment, this is the test to pursue.
Where to Get Tested
You have several options for where to go, each with different costs and convenience tradeoffs.
- Your primary care doctor or OB-GYN: Can order either a swab (if you have symptoms) or a blood test. Insurance typically covers STI testing when there’s a clinical reason for it, though coverage varies.
- Public STD clinics: Most cities have publicly funded clinics that test for herpes among other STIs. For uninsured patients, fees often run on a sliding scale. At Denver Health’s STD clinic, for example, routine testing costs $20 to $90 without insurance. Many clinics offer even lower fees based on income.
- Planned Parenthood and community health centers: These offer herpes testing and can usually process both swab and blood tests. Sliding-scale pricing is common.
- Online lab orders: Services like STDcheck, Everlywell, or LetsGetChecked let you order a blood test online and visit a local lab for the blood draw, or send in a sample from home. However, at-home herpes blood tests carry the same false-positive concerns as any IgG screening. No at-home herpes test has received FDA approval. The only FDA-approved home STI tests cover HIV, syphilis, and a combined chlamydia/gonorrhea/trichomoniasis test for women.
What to Know Before You Test
Herpes testing is not part of standard STI screening panels. If you go in for a routine checkup and your doctor says “your STI tests were all clear,” herpes was almost certainly not included. You need to ask for it specifically. This is partly because blood tests for herpes produce enough false positives that screening everyone, regardless of symptoms or risk, can cause more confusion than clarity.
That said, there are good reasons to request a test: you have a partner who’s been diagnosed, you’ve had a suspicious sore, you’re starting a new sexual relationship and want a complete picture, or you had unprotected contact with someone whose status is unknown. In any of these situations, being direct with your provider about wanting HSV testing will ensure it’s included.
If your result comes back positive with a high index value (above 3.50) or is confirmed by Western blot, the result is reliable. If it comes back negative and at least 16 weeks have passed since your last potential exposure, that’s also reliable. The gray zone is the low-positive range, and the solution there is confirmatory testing rather than accepting the result at face value.