How accurate are blood tests for Herpes?

When it comes to testing for sexually transmitted infections (STIs), accuracy matters. Many people searching “how accurate are blood tests for Herpes?” are looking for reassurance that their results can be trusted.

Herpes is very common, often symptom‑free, and frequently misunderstood. Blood testing plays an important role in diagnosing Herpes when symptoms are absent, but, like all medical tests, it has limitations. Understanding how these tests work, when to take them, and what your results really mean can help you make informed decisions about your sexual health.

In fact, across Better2Know’s dataset of standalone Herpes tests, 100% of patients chose a laboratory‑based IgG blood test, with 0% relying on visual lesion swabs alone. This clear preference highlights just how important definitive, medical‑grade accuracy is when it comes to Herpes testing.

STI test results can affect your peace of mind, your relationships, and sometimes your treatment choices. An inaccurate result can either cause unnecessary anxiety or provide false reassurance.

This is especially true for Herpes, where many people never develop obvious symptoms. Accurate testing helps you understand your exposure history, reduce the risk of passing the infection to others, and take control of your sexual health with confidence.

Herpes is a viral infection caused by the Herpes simplex virus (HSV). There are two main types:

• HSV‑1, which most commonly causes oral Herpes (cold sores)
• HSV‑2, which more commonly causes genital Herpes

Both types can be passed through skin‑to‑skin contact, including oral, vaginal, and anal sex. Once infected, the virus remains in the body for life, although symptoms may come and go, or never appear at all. This is one of the reasons testing can be complicated.

There are two main ways to test for Herpes:

• Swab tests, which take a sample from a visible blister or sore
• Blood tests, which look for antibodies produced by the immune system in response to HSV

A blood test to detect IgG antibodies can provide interesting and useful information about a Herpes infection. However, PCR testing remains the definitive standard for detecting Herpes in most circumstances.

Timing plays a crucial role in Herpes testing accuracy.

After infection, it takes time for your body to produce detectable antibodies. This period is known as the window period. Testing too early can result in a false negative.

It’s important to speak to a medical professional about your situation, since the type of test you get will depend on your individual circumstances. A PCR test will be recommended in most cases, but a blood test may be useful in certain situations.

If you have visible sores or blisters, a swab test is usually the most accurate way to diagnose Herpes. This is because the sample is taken directly from the affected area and can detect the virus itself.

However, swabs are only effective when symptoms are present. Once sores begin to heal, accuracy decreases. Blood tests remain the best option when symptoms are absent or have already resolved.

If I test negative, should I get tested again?

Medical opinion is paramount if you are experiencing symptoms. If you get tested with Better2Know, we will connect your with a private doctor who can help guide you through the next steps.

So, how accurate are blood tests for Herpes? When taken at the right time and properly interpreted, they can be a helpful tool to help aid the detection of prior exposure to HSV, especially when no symptoms are present.

At Better2Know, we use laboratory‑based Herpes blood tests designed to deliver reliable, confidential results, along with expert support to help you understand what those results mean. If you are unsure about the best test for you, our team is always here to help.

This article has been medically reviewed by Dr. Steve Chapman, 13/07/2026.