What does a positive herpes IgM test result mean?

Herpes IgM (Immunoglobulin The M) test is a blood test that can detect early herpes simplex virus (HSV) infection. HSV is an infectious disease that causes ulcers around the mouth or genitals.

The IgM test does not directly detect herpes. Instead, it looks for IgM, an antibody. This is a protein produced by the immune system in response to a herpes infection.

This article discusses the purpose of the herpes IgM test and what the results mean.

Testing purposes

Herpes IgM tests are usually done to confirm whether a person has herpes after an outbreak. The test is a simple blood test and results are usually available within a week.

It takes time for the test to become positive. However, herpes IgM is one of the first types of antibodies to appear after infection. Therefore, it is the earliest blood test available to detect herpes. The herpes IgG antibody test will become positive later in the infection.

A direct swab test of herpes lesions may be able to detect the virus more quickly. However, the time to directly detect the virus in sores is limited.

If you think you may have been exposed to herpes, you may not want to seek immediate medical attention. This is because it can take up to 10 days for herpes IgM antibodies to develop after initial infection with the virus.

If you think you’ve been exposed to the virus but don’t have any symptoms, you should wait At least Two weeks before being tested. It may be wise to wait longer, depending on what tests are available in your area.


Herpes IgM antibodies are among the first antibodies to appear after a herpes infection, usually after 10 days. Therefore, an IgM test can detect herpes earlier than an IgG blood test.

How to know if you have herpes

Interpret the results

The results of the herpes IgM test are usually reported as positive, negative, or equivocal.

Herpes IgM Test Results

  • A positive test result means herpes IgM was detected in the sample.
  • A negative result means no IgM is detected.
  • An equivocal test result means the test cannot determine the presence of antibodies.

Is it a new infection or a recurring infection?

Common sense suggests that a positive herpes IgM blood test means someone has recently had herpes. However, that’s not all.

Herpes IgM levels tend to rise early in infection, and levels typically fall over time. This means that a positive herpes IgM result is usually associated with a new infection. However, this was not the only time IgM could be detected.

people who have recently had herpes Do Tends to have a positive HSV IgM test. The same is true for many people with recurrent (recurrent) herpes infections. Between 30% and 70% of people with recurrent herpes test positive for HSV IgM, depending on the test and study.

In other words, an IgM test without any other data does not prove that the herpes infection was recent. This is especially true if accompanied by a positive herpes IgG test.

People don’t test positive for HSV IgG until at least a few months after infection. However, IgG levels are expected to remain high throughout infection, while IgM levels are expected to vary widely.

Therefore, if someone tests positive for both IgG and IgM, they may relapse. It’s almost certainly not a new infection. A positive IgM test alone is more likely to be a new infection.


A positive IgM test could mean you have a new HSV infection. It may also mean that you have repeated infections, especially if your IgG test is also positive.

Interpreting a positive herpes IgG test

false positive result

Blood tests for herpes can give false positives, especially in areas where relatively few people have herpes.

You may not be infected at all. Or you may have another virus that stimulates antibodies that cross-react with the herpes test. This could include the Epstein-Barr virus in the herpesvirus family or the parvovirus that causes fifth disease.

So if you don’t have any symptoms, you may want to get an IgG test at a later time. If you do have symptoms, your healthcare provider can test for herpes lesions directly. There is no need to wait for an antibody response.

The herpes IgM test does carry a risk of false positive results. Health care providers may be reluctant to offer testing if you do not have herpes symptoms. A positive result is more likely to be accurate if you have symptoms of a herpes outbreak.

follow up

If you don’t get regular screenings, you may need to have a repeat test after six months. That way, you’re more likely to identify an infection without missing the window where the test was accurate.


The herpes IgM test can detect early HSV infection by looking for IgM antibodies. After HSV infection, your body produces IgM and IgG antibodies. IgM antibodies usually appear first, so an IgM test can detect it earlier than an IgG test.

IgM tests can usually start detecting HSV about 10 days after infection. A positive IgM test may mean you have a new or recurrent HSV infection. If you have a positive IgM test and a negative IgG test, you may have a new infection.

To verify your test results, consider following up with your healthcare provider within six months for a repeat test.

Frequently Asked Questions

  • What are HSV IgG and HSV IgM?

    HSV IgG and HSV IgM are antibodies raised against the herpes simplex virus. A blood test can look for these antibodies to diagnose herpes. Herpes IgM is one of the first antibodies produced after infection and is the first blood test available to detect herpes. Herpes IgG does not become positive until later in the herpes infection.

  • What does HSV IgM positive mean?

    A positive HSV IgM blood test indicates the presence of herpes immunoglobulin M. This means that the person has the herpes virus. HSV IgM usually appears in the early stages of herpes infection, but usually declines in the later stages. You can test negative for HSV IgM and still have herpes.

  • What does HSV IgG positive mean?

    A positive HSV IgG blood test indicates the presence of herpes immunoglobulin G. This means that the person has the herpes virus. HSV IgG is an antibody that is produced several months after a person is initially infected with herpes. In the early stages of infection, the HSV IgG test will not be positive.

  • Does a positive HSV IgM test mean the herpes infection is new?

    possible. However, if both HSV IgM and HSV IgG are positive, the herpes virus has been present for at least a few months.