HSV-2 IgG/IgM Antibody Test: What You Need to Know

What Is the HSV-2 IgG/IgM Test?

I recently saw a 32-year-old woman in my clinic. She was anxious about a new partner’s herpes history and had no symptoms, but wanted definitive answers. We talked about the HSV-2 IgG/IgM test—a blood test that looks for antibodies your immune system makes against herpes simplex virus type 2. This test can tell whether you’ve been exposed to HSV-2 in the past (IgG) or have a very recent or active infection (IgM). In my practice, I find this test especially helpful when someone has no sores but is worried about transmission.

When Is This Test Ordered?

Common reasons include:

• Unexplained genital sores or blisters (to confirm HSV-2)
• Screening during pregnancy (to prevent neonatal herpes)
• Partner with known HSV-2—checking your own status
• Recurrent symptoms suggestive of herpes but with negative swab tests
• Before immunosuppressive therapy or organ transplant

Understanding Your Results: IgG vs. IgM

Most labs report results as negative, equivocal, or positive based on an index value. IgG antibodies usually appear 2–4 weeks after infection and stay in your blood for life—a positive IgG means past or chronic infection. IgM antibodies appear earlier (within days) and often disappear after a few months, but they are not very specific. In my clinical experience, a positive IgM alone should be interpreted cautiously because it can cross-react with other viruses.

Reference Range Table

Note: Ranges vary by laboratory. Always check your specific lab’s reference.

What Does a Positive HSV-2 IgG Mean?

A positive IgG result generally indicates you have been infected with HSV-2 at some point. Most people with positive IgG never have symptoms—this is called asymptomatic shedding. You can still transmit the virus even without sores. If you have no history of outbreaks, a positive IgG can be emotionally challenging. I always reassure my patients that many couples manage this with condoms, suppressive therapy, and open communication.

False Positive HSV-2 Test: Is That Possible?

Yes, false positives can happen, especially with older IgG tests. The CDC recommends confirmatory testing (like the Western blot) if the index value is low (1.1–3.5) and you have no risk factors or symptoms. In my practice, I’ve seen several patients who tested “positive” on a routine screen only to later learn it was a false alarm. Confirmatory testing is key to avoid unnecessary stress.

HSV-2 IgM: When Is It Useful?

IgM testing is controversial. Many experts, including those at the CDC, do not recommend routine IgM for diagnosing genital herpes because it can remain positive for months and cross-reacts with other herpes viruses (like varicella-zoster). I rarely use IgM in my clinic. If you have a new sore, a PCR swab is far more accurate. IgM is sometimes used in research or in neonatal cases.

HSV-2 and Pregnancy

If you’re pregnant and have a history of genital herpes, your doctor may check HSV-2 IgG to assess risk. A negative IgG means no prior infection—but you can still acquire it during pregnancy, which is dangerous for the baby. A positive IgG with no active lesions usually leads to a safe vaginal delivery. However, if you have active sores at the time of labour, a Caesarean section is often recommended to protect the newborn. I advise all my pregnant patients to discuss herpes testing early in pregnancy.

Can HSV-2 Be Cured?

There is no cure for HSV-2. The virus stays in your nerve cells for life. But antiviral medicines (acyclovir, valacyclovir, famciclovir) can control outbreaks, reduce symptoms, and lower the chance of passing it to a partner. Many people take daily suppressive therapy. In my experience, most patients with HSV-2 lead normal, active lives with proper management.

How Is the Test Performed?

It’s a simple blood draw, just like any other routine lab test. No special preparation is needed. Results usually come back within a few days. If you have symptoms, your doctor will also likely swab any sores for PCR testing—that’s the gold standard for diagnosing active herpes.

What Should You Do After Getting Your Results?

If you test positive, don’t panic. Talk to your doctor about whether you need suppressive medication, how to reduce transmission, and how to tell a partner. If you test negative but have symptoms, repeat testing or a PCR swab may be warranted. In my clinic, I always pair blood results with a full sexual health conversation—because knowledge empowers prevention.