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Herpes (HSV) Test
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Herpes (HSV) Test

A herpes test identifies the presence of the herpes simplex virus (HSV) through either a swab of a sore or a blood test.

What is a herpes (HSV) test?

A herpes test looks for signs of the herpes simplex virus (HSV). There are two main types:

  • HSV-1: Usually causes oral herpes (cold sores). It is often spread through non-sexual contact with saliva.
  • HSV-2: The most common cause of genital herpes, which is a sexually transmitted infection (STI) spread through sexual contact.

There is no cure for HSV, but medicines can manage outbreaks. If you are pregnant, it is important to know your status, as the virus can be passed to a fetus or newborn.

What is it used for?

Testing methods depend on whether symptoms are present:

  • If sores are present: A provider collects fluid from the sore using a swab. This is tested via a viral culture (growing the virus in a lab) or a polymerase chain reaction (PCR) test (looking for genetic material).
  • If no sores are present: A blood test looks for HSV antibodies, which are proteins the immune system creates to fight the virus.

Why do I need an HSV test?

Testing is typically recommended if you have symptoms such as blisters or sores, fever, flu-like symptoms, swollen glands, or pain/tingling in the affected area. Medical experts generally do not recommend testing for people without symptoms. However, you may be at higher risk and require testing if you have multiple sexual partners, other STIs, HIV, or engage in unprotected sex.

What do the results mean?

  • Negative/Normal: Signs of the virus were not found. Note that blood tests for antibodies may be negative if performed too soon after infection, as it can take up to three months for the body to produce them.
  • Positive/Abnormal: Signs of HSV were found. If a blood test is positive for antibodies, it indicates either an active or past infection.

If you test positive, talk to your provider about treatment to control symptoms and reduce the risk of spreading the virus. Because HSV can increase the risk of acquiring HIV, your provider may recommend additional STI testing.

Frequently Asked Questions

Knowing your HSV status is crucial during pregnancy because primary infection in the third trimester carries the highest risk of transmitting the virus to the newborn, which can cause severe neonatal herpes. If you test positive, your provider will likely prescribe antiviral medication (such as acyclovir) starting at 36 weeks of gestation to reduce the risk of an outbreak during labor. If you have an active outbreak or prodromal symptoms at the time of delivery, a cesarean section is typically recommended to prevent transmission to the baby. If you test negative, you should avoid exposure to new partners during pregnancy to prevent primary infection.
negative blood test indicates that no antibodies were detected at the time of the test, but it does not guarantee you are virus-free, especially if the test was taken during the window period. Furthermore, HSV can be transmitted through asymptomatic shedding, where the virus is active on the skin surface without visible sores. To reduce transmission risk, it is recommended to use barrier methods (condoms or dental dams) and to avoid sexual contact if you notice any prodromal symptoms like tingling or itching. Discussing your status and testing history with your partner is essential for informed consent and safety.
PCR (polymerase chain reaction) test detects the genetic material of the virus and is considered the gold standard for accuracy, with sensitivity rates often exceeding 95 percent. A viral culture involves growing the virus in a lab and is less sensitive, particularly if the sore is older than 48 hours or if the sample is not collected properly. Because PCR can detect the virus even when it is not actively replicating in high numbers, it is preferred for diagnosing active outbreaks and for distinguishing between HSV-1 and HSV-2.
Blood tests detect antibodies, which take time for the immune system to produce. It can take 2 to 12 weeks after the initial infection for antibodies to reach detectable levels. If you test negative shortly after a first outbreak, the result may be a false negative. In this case, a swab test (PCR or culture) taken directly from an active sore is far more accurate for diagnosis. If you have no active sores and a negative blood test, your provider may recommend retesting after 3 months to ensure antibodies have had sufficient time to develop.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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