What Is a Herpes IgG Test?

An IgG blood test is used to diagnose herpes simplex virus (HSV) infection. This test does not detect the virus. Rather, it detects the IgG antibodies, or immune proteins, that your body produces in response to the viral infection.

Parts of the IgG protein, like all antibodies, are made by the immune system to attack specific disease-causing organisms (pathogens), like viruses and bacteria. HSV IgG is the type of antibody that is produced when a herpes infection occurs.

This article discusses the IgG blood test and how it can determine if you have herpes simplex virus (HSV).

Purpose of Test

An HSV IgG test is typically used to confirm a genital herpes infection. It is not recommended as a general screening test for everyone. But it is recommended for pregnant women who are at risk of having genital herpes. Treatment can reduce the risk of transmission to the baby.

It can be performed alongside:

• A viral culture, in which the actual pathogen is grown in a lab
• HSV polymerase chain reaction (PCR), which can detect the genetic material (DNA) that makes up the herpes virus

Both of these tests are done using a sample of fluid taken from an open sore.

It can take three to six weeks from the initial infection before enough IgG is produced to be detected.

IgG vs. IgM

The IgG test is not the only antibody test used to detect HSV. There's also an HSV immunoglobulin M (IgM) test, which detects IgM.

Unlike IgG antibodies that stay in the body and can be detected for a lifetime, IgM antibodies don't last very long. They usually can only be detected during an active or recent infection.

Another advantage of the IgG test is that it's more accurate when it comes to telling the difference between HSV-1 and HSV-2. HSV-1 is the type of herpes primarily associated with cold sores. HSV-2 is the type that mainly causes genital herpes.

Risks and Contraindications

There are no reasons why someone can't have an IgG test. The risks associated with the procedure are very low.

Before the Test

This test requires no preparation, and it only takes a few minutes.

Timing

The minimum time period between contact with HSV and the production of detectable antibodies, what's called the window period, is four to six weeks after the suspected exposure. Testing any time earlier would likely return a negative result unless you have been infected with HSV before.

If you have clinical signs of an infection and your HSV IgG test is negative, repeat the test in about four to six weeks to confirm the results. The test will also determine which type of HSV virus you may have acquired.

Location

HSV antibody blood tests may be offered at:

• Sexually transmitted infection (STI) clinics
• Women's health clinics
• Pathology labs
• Retail blood testing centers
• Public clinics
• Some human immunodeficiency virus (HIV) service organizations

While some of these centers offer drop-in testing, others may require an appointment and/or a referral. Call in advance for details and to confirm that they provide the IgG test.

Food and Drink

There are no food or drink restrictions you need to follow before having this test.

Cost and Health Insurance

Depending on where you live and the lab you use, your HSV IgG blood test can cost between $35 and $80. Public clinics tend to be cheaper.

Genital HSV is considered an STI. But don't assume that a free STI clinic will have the test or provide it free of charge. Some may only offer free testing for:

• HIV
• Hepatitis
• Select STI screening tests

What to Bring

If using a public clinic, the facility may require a government-issued ID to confirm your residency. Call in advance for details.

You should also check to see if they accept your insurance, if you're enrolled in a plan.

Bring your insurance card (if applicable) and a method of payment.

During the Test

Upon arrival at the testing site, you will be asked to register, sign a consent form, and possibly confirm your insurance information.

Because genital HSV is not what's called a notifiable disease, like HIV or hepatitis, your information and results will not be shared with local, municipal, state, or federal health authorities.

Pre-Test

Some STI clinics will conduct a short pre-test counseling. The aim of the counseling is to establish why you feel you need the test and whether you may be at risk of other STIs.

Based on your response, the counselor may recommend additional STI screening. The recommendations do not have anything to do with you personally. They are based on guidelines for all people in highly affected populations.

This includes chlamydia and gonorrhea testing for sexually active women under age 25, women ages 25 and older, and men with certain risk factors. They may also offer HIV testing, which is recommended once for all people ages 15–65.

Throughout the Test

An HSV blood test is a simple blood draw involving the following steps:

1. An elastic band is placed around your upper arm to make a selected vein swell.
2. The injection site is cleaned with an antiseptic swab.
3. A needle is inserted into the vein.
4. Between 8 milliliters and 10 milliliters of blood is extracted into a vacuum-sealed test tube.
5. The needle is removed, and your arm is bandaged.
6. The tube is sent to a lab for evaluation.

After the Test

You will have a small puncture wound at the injection site. This should stop bleeding within a few minutes. Leave the bandage on for about one day to prevent infection.

While it isn't common, you might have soreness, swelling, and/or bruising at the injection site. Light-headedness and infection are rare but also possible.

HSV-1 IgG Test Results Interpretation

An HSV test with a positive (abnormal) IgG result means that you either have or have had an HSV infection at some point. Since a positive result means that your body has built an IgG immune response to HSV, a negative IgG test means that your body has never needed to do so and you have never been infected with HSV.

Your test results should be ready within two to five working days. Timing may vary depending on the clinic or lab.

The results of your HSV blood test will generally be reported as either:

• Positive: IgG detected
• Negative: IgG not detected
• Equivocal: Results unclear

If your test is equivocal, your healthcare provider might consider results of other tests you've had done to make your diagnosis. They might also recommend that you repeat the IgG test after a few weeks.

IgG results may be considered along with IgM results. IgG antibodies take longer to produce but last a lifetime. IgM antibodies are detectable after a few days, but they disappear within a few weeks.

• If you test positive for IgG and IgM, or just IgM, it's likely that you have a new infection.
• If you test positive for IgG but not IgM, you likely have an existing infection that has been around for at least two months.
  

That said, between 30% and 70% of people with recurrent infections test positive for IgM, according to a 2014 review published in the Virology Journal.

A false-negative result, in which your test result is incorrectly reported as negative for HSV antibodies, can sometimes occur. This happens, for instance, if you have your test within the window period, not allowing enough time to pass after a possible exposure. You may also have a false-positive result, in which the test result incorrectly reads as positive.

Summary

An IgG blood test is used to diagnose herpes simplex virus infection. It detects the antibodies your body produces to fight against the virus.

It can take three to six weeks from the initial infection before enough IgG is produced to be detected. Test results are ready within two to five working days.

A Word From Verywell

If you have symptoms of HSV, it's important that you get medical attention. Your healthcare provider can examine you and order the appropriate tests.

It can be overwhelming to even think about the possibility of an HSV diagnosis. But if you are positive, know that you are not alone. According to the CDC, more than one out of every six people ages 14–49 years old has genital HSV.

It is important to remember that you can live a long and happy life with herpes. Seek treatment early and follow your healthcare provider's guidance on safer sex.