HSV IgG Blood Test: What It Measures, How to Read Your Results, and What Comes Next

Reviewed by HealthMatters Clinical Review Team · Last updated February 2026

Key Takeaways

• The HSV IgG test detects past exposure to herpes simplex virus — it does not diagnose an active outbreak or tell you when you were infected
• A positive result does not mean you are currently contagious, will develop symptoms, or need treatment
• HSV-1 and HSV-2 are distinct viruses — the type-specific IgG test tells you which one (or both) you have encountered
• IgG antibodies take 3–6 weeks to appear after initial infection — testing too early produces false negatives
• HSV is extremely common: roughly 67% of adults worldwide have HSV-1, most without ever knowing it

If you have just received an HSV IgG blood test result and are not sure what it means, you are in the right place.

The HSV IgG test does not detect the herpes virus itself — it detects whether your immune system has ever responded to it. A positive result means your body has encountered herpes simplex virus (HSV) at some point in the past. It does not mean you have an active infection right now, that you are currently contagious, or that you will necessarily develop symptoms. The vast majority of people who test positive live entirely normal lives without ever requiring treatment.

The test comes in two type-specific forms: HSV-1 IgG and HSV-2 IgG. Understanding which type you have been exposed to — and what that actually means for your health — is what this page is for.

How common is HSV?

HSV is one of the most prevalent infections on the planet, and most people who carry it have no idea.

According to the World Health Organization, approximately 3.7 billion people under age 50 — roughly 67% of the global population — are infected with HSV-1. The majority acquired it in childhood through everyday non-sexual contact such as a kiss from a family member or sharing a drink. HSV-2, which is most commonly associated with genital herpes, affects an estimated 491 million people aged 15–49 worldwide. In the United States, the CDC estimates that approximately 12% of people aged 14–49 have HSV-2.

Most people who test positive for HSV antibodies were completely unaware they carried the virus. A positive IgG result is one of the most common findings in routine blood testing, and by itself it is rarely a medical emergency.

What does the HSV IgG test actually detect?

The HSV IgG test is an antibody test, not a viral detection test. Here is the distinction:

When your body encounters HSV for the first time, your immune system responds by producing proteins called antibodies that target the virus. IgG (immunoglobulin G) antibodies are one class of these proteins. They take several weeks to develop after initial infection, but once they appear, they remain in your bloodstream for life — even when the virus is completely dormant and you have no symptoms.

This means the IgG test is a record of past exposure, not a measurement of current viral activity. A positive result tells you: at some point, your immune system encountered this virus and built a response to it. It does not tell you when that happened, whether the virus is active, or where in your body the infection resides.

The test is type-specific, meaning it can distinguish between:

• HSV-1: Most commonly associated with oral herpes (cold sores, fever blisters). Can also cause genital herpes through oral-genital contact.
• HSV-2: Most commonly associated with genital herpes. Less frequently causes oral herpes.

Type-specific testing is important because the two viruses behave differently, have different recurrence rates, and carry different implications for partners and pregnancy.

What is the difference between IgG and IgM herpes antibody tests?

You may see both IgG and IgM antibody tests ordered together. They measure different things:

Why IgM results are often misleading

IgM is sometimes marketed as a way to detect "new" or "recent" herpes infections. In practice, it is far less reliable than this implies. Research has shown that between 30% and 70% of people with recurrent HSV infections test positive for IgM during reactivations — meaning a positive IgM result does not confirm that an infection is new. IgM can reappear months or years after the original infection whenever the virus reactivates.

The CDC and most infectious disease specialists do not recommend using IgM results alone to determine whether an HSV infection is recent. If establishing infection timing is clinically important — for example, during pregnancy — a Western Blot confirmatory test is the more reliable approach.

How to interpret combined IgG and IgM results

How do you read an HSV IgG test result?

Results are reported as an index value — a number that reflects how much antibody activity was detected. Most labs use the following ranges, though exact cutoffs vary slightly between laboratories. Always compare your result to the reference range printed on your specific lab report.

Does the index value number matter — is a higher number worse?

No. The magnitude of a positive index value does not indicate how severe your infection is, how recently you were infected, or how likely you are to have symptoms. A result of 5.0 is not "worse" or more infectious than a result of 1.5. Both are simply positive — meaning antibodies were detected. The number reflects the sensitivity of the antibody response, not the severity of the condition.

How accurate is the HSV IgG test?

The HSV-1 IgG test is generally considered highly accurate, with specificity above 97% in most studies. The HSV-2 IgG test is somewhat less reliable at low positive values.

False negative results

A false negative — where you have HSV but the test shows negative — most commonly occurs when testing happens too soon after exposure. IgG antibodies require 3–6 weeks to reach detectable levels after initial infection. In some individuals, full seroconversion takes up to 12 weeks. If you had a recent potential exposure and your result is negative, retesting after 6–12 weeks is recommended.

False positive results — especially for HSV-2

False positives are uncommon for HSV-1 but are a documented issue for weakly positive HSV-2 results. Research has shown that index values in the 1.10–3.49 range on some commercial HSV-2 IgG assays have a significantly higher rate of false positives than strongly positive results. In some published studies, up to 50% of weakly positive HSV-2 IgG results did not confirm on Western Blot testing.

If your HSV-2 IgG result is weakly positive (roughly 1.10–3.49) and you have no symptoms or known exposure history, ask your doctor about confirmatory Western Blot testing before drawing any conclusions. This is especially important before disclosing a diagnosis to a partner.

Why would a doctor order an HSV IgG test?

The HSV IgG test is used in specific clinical situations — it is not recommended as a routine screening test for the general population. Doctors may order it to:

• Investigate recurrent cold sores or unexplained oral lesions
• Evaluate genital sores, ulcers, or lesions
• Distinguish between HSV-1 and HSV-2 in a confirmed herpes diagnosis
• Screen during pregnancy — particularly in women at risk of genital HSV, where transmission to the newborn during delivery is a serious concern
• Assess transmission risk between partners where one partner has a known HSV diagnosis
• Investigate symptoms in immunocompromised individuals where HSV may behave differently

The CDC advises against routine HSV IgG screening for asymptomatic individuals who have no known exposure, noting that the psychological impact of an unexpected positive result often outweighs the clinical benefit in people with no symptoms.

What symptoms are associated with HSV-1 and HSV-2?

The majority of people infected with HSV have mild symptoms or none at all. When symptoms do occur, they typically vary by virus type.

HSV-1 symptoms (most commonly oral)

• Cold sores or fever blisters on or around the lips
• Tingling, itching, or burning before a sore appears
• Painful mouth sores during a first infection
• Swollen lymph nodes and mild fever during primary infection

HSV-2 symptoms (most commonly genital)

• Blisters, sores, or ulcers in the genital or anal area
• Burning or pain during urination
• Flu-like symptoms (fever, muscle aches, headache) during first infection
• Recurrent outbreaks — typically shorter and milder than the first

A positive IgG result in the absence of any of these symptoms is extremely common and, in most cases, does not require treatment.

How is HSV transmitted?

HSV spreads through direct contact with infected skin or mucosal surfaces. Transmission can occur even when no visible sores are present — a phenomenon called asymptomatic shedding.

• HSV-1 most commonly spreads through kissing, oral contact, or sharing items like utensils or lip products. It can be transmitted to the genitals through oral-genital contact.
• HSV-2 most commonly spreads through genital-to-genital or genital-to-oral contact.

Risk of transmission is highest during active outbreaks, but the virus can be shed — and transmitted — at any time.

What is the difference between HSV-1 and HSV-2?

How is HSV treated and managed?

There is no cure for HSV — once the virus enters the body, it remains in the nervous system permanently, typically in a dormant state. However, it is very manageable.

Antiviral medications

Three antiviral medications are commonly used to reduce outbreak severity, frequency, and transmission risk:

• Acyclovir — the original antiviral, taken multiple times per day
• Valacyclovir (Valtrex) — a prodrug of acyclovir, taken less frequently, often preferred
• Famciclovir — similar efficacy, alternative option

These can be used as episodic therapy (taken at the start of an outbreak) or suppressive therapy (taken daily to reduce outbreaks and lower transmission risk to partners).

Common outbreak triggers

• Physical or emotional stress
• Illness, fever, or immune suppression
• Sun or UV exposure (particularly for oral HSV-1)
• Hormonal changes (menstrual cycle)
• Fatigue or sleep disruption
• Skin trauma in the affected area

Many people with HSV never require medication and manage the condition entirely through lifestyle awareness.

What should you do after your HSV IgG test result?

If your result is negative

No action is required. If you had a potential exposure within the last 6 weeks, your IgG antibodies may not have had time to develop. Consider retesting 6–12 weeks after the potential exposure to confirm.

If your result is equivocal (0.91–1.09)

Do not treat this result as positive or negative. Wait 3–4 weeks and retest. A single equivocal result is not clinically meaningful on its own.

If your result is positive for HSV-1

This is extremely common — the majority of the world's adult population has HSV-1. If you have no symptoms, no treatment is required. If you experience frequent cold sores, antiviral suppression therapy can significantly reduce their frequency and severity. If you are pregnant, mention this result to your OB.

If your result is positive for HSV-2

Speak with your doctor, particularly if you have genital symptoms. Antiviral therapy can reduce outbreak severity and frequency. If you have a sexual partner, discuss transmission risk — daily suppressive therapy with valacyclovir reduces the risk of transmission to an uninfected partner by approximately 50%.

If your HSV-2 result is weakly positive (index 1.10–3.49)

Ask your doctor about Western Blot confirmatory testing before making any decisions, disclosing a diagnosis to a partner, or beginning treatment. Weakly positive HSV-2 IgG results carry a documented rate of false positives on some commercial assays.

If you are pregnant

HSV in pregnancy requires careful management, particularly near delivery. Discuss your results with your OB or midwife regardless of whether you have symptoms. Suppressive antiviral therapy from 36 weeks onward is commonly recommended for women with known genital HSV to reduce the risk of neonatal transmission.

When should you speak with a doctor about your HSV result?

A positive HSV-1 IgG without symptoms is usually not a reason to contact your doctor urgently. However, speak with a healthcare provider if:

• You have genital sores, blisters, or unexplained ulcers
• You have frequent or severe cold sores affecting your daily life
• You are pregnant or planning to become pregnant
• You are immunocompromised (HIV, organ transplant, chemotherapy)
• You have a new partner and want to discuss transmission risk
• Your HSV-2 result is weakly positive and you want confirmatory testing
• You had a potential recent exposure and tested negative — retesting is recommended

Frequently asked questions about the HSV IgG test

What does a positive HSV IgG result mean?

A positive HSV IgG result means your immune system has produced antibodies to herpes simplex virus, indicating past exposure. It does not mean you have an active infection, that you are currently contagious, or that you will develop symptoms. Most people with positive HSV-1 IgG acquired it in childhood and live without symptoms or complications.

Can HSV IgG antibodies go away over time?

No. IgG antibodies to HSV remain detectable for life. Once you test positive for HSV IgG, that result will not revert to negative. The antibody level may fluctuate slightly over time, but it will remain above the positive threshold. A future negative result would most likely indicate a laboratory error or a different test methodology being used.

Is a high HSV IgG index value more serious than a low positive?

No. The magnitude of a positive index value does not correlate with severity, contagiousness, or recurrence frequency. A result of 8.0 is not more serious than a result of 1.2. Both indicate past exposure. The number reflects antibody concentration in the blood sample, not the severity of infection.

Can you have a false positive on an HSV IgG test?

Yes, though it depends on the test type. False positives are uncommon for HSV-1 IgG (specificity above 97%). For HSV-2 IgG, weakly positive results in the 1.10–3.49 index range have a documented false positive rate on some commercial assays. If you have a weakly positive HSV-2 result with no symptoms or known exposure, Western Blot confirmatory testing is worth discussing with your doctor.

How long after exposure will the HSV IgG test turn positive?

IgG antibodies typically become detectable 3–6 weeks after initial HSV infection, though in some individuals full seroconversion can take up to 12 weeks. Testing within the first few weeks of a suspected exposure may produce a false negative. If you suspect recent exposure, retest 6–12 weeks afterward for a reliable result.

Can I have HSV-1 IgG antibodies and never have had a cold sore?

Yes — this is extremely common. Most people who test positive for HSV-1 IgG have never had a recognizable cold sore, or had symptoms so mild they attributed them to something else. HSV-1 is typically acquired in childhood through non-sexual contact, and the majority of carriers experience no noticeable outbreaks throughout their lives.

Should I tell my partner if my HSV-1 IgG is positive?

This is a personal decision and there is no universal medical requirement to disclose. HSV-1 is present in roughly 67% of adults, and most people have been exposed without knowing it. Many clinicians do not consider a positive HSV-1 IgG result — particularly without symptoms — to carry significant disclosure obligations. HSV-2, which is less prevalent and more strongly associated with symptomatic genital herpes, generally warrants a more direct conversation with sexual partners. Discuss your specific situation with your doctor.

Is the HSV IgG test the same as the Western Blot test?

No. The standard HSV IgG test is an ELISA (enzyme-linked immunosorbent assay) — a widely available commercial blood test. The Western Blot is a more specialized and more accurate test used to confirm uncertain or weakly positive ELISA results. The Western Blot is considered the gold standard for HSV antibody testing but is only available through specific reference laboratories and is not routinely ordered.

Explore specific HSV IgG test results

For detailed interpretation of your specific test result, visit the individual biomarker pages:

• HSV-1 IgG Type Specific — what your result means
• HSV-2 IgG Type Specific — what your result means

Track your HSV IgG results over time alongside your other lab values. Upload your report to HealthMatters to store, compare, and share securely with your doctor.