Skip to content
Blood Test Tracker

Herpes Simplex Virus 1 IgG (Type-Specific)

Looks for IgG antibodies to herpes simplex virus type 1 (HSV-1), the usual cause of cold sores. A positive result means you were infected at some point.

AI-verified against cited sources. Awaiting expert reviewAlso called HSV-1 IgG, HSV1 IgGLOINC 7909-5

What it is

Herpes simplex virus type 1 (HSV-1) is very common. It mostly causes cold sores around the mouth, but it can also infect the genitals. Many people have it without ever having symptoms. This blood test looks for IgG antibodies that your body makes after infection. Labs usually report an index value with a label of negative, equivocal or positive. In a US government survey, about 48% of people aged 14 to 49 had HSV-1 antibodies in 2015 to 2016.

Why it matters

A positive result shows past exposure to HSV-1, which is very common and often causes no symptoms. CDC says HSV-1 blood tests cannot tell whether the infection is in the mouth or the genitals, and that they usually should not be used to diagnose genital HSV-1. If you have a sore, a swab test of the sore is the usual way to find the cause. Because a positive result is so common, your clinician will read it alongside your symptoms and history.

If it’s high

A positive result means HSV-1 antibodies were found, which is usually a sign of a past or current HSV-1 infection. This is common: about 48% of people aged 14 to 49 in the US tested positive in 2015 to 2016, and the share rises with age. The test cannot say when you were infected, where on the body, or whether you will ever have symptoms.

Common causes

  • A past HSV-1 infection, often picked up in childhood or young adulthood and often without symptoms
  • Cold sores around the mouth
  • HSV-1 infection of the genitals, which this test cannot tell apart from an oral infection

What can help

  • Ask your clinician whether the result changes anything for you
  • If you have a sore, ask about a swab test of the sore
  • If you are pregnant or planning pregnancy, ask what a positive result means for your care

What can affect your result

  • Age: positive results become more common with age (about 27% at ages 14 to 19 and about 60% at ages 40 to 49 in US data)
  • Time since infection: antibodies take weeks to appear
  • Test sensitivity: CDC notes HSV-1 antibody tests have low sensitivity
  • Test brand: index cutoffs and equivocal zones differ
  • The test cannot show where on the body the infection is
  • Testing soon after infection can be negative, because antibodies take weeks to appear. For HSV-2, CDC advises repeating the antibody test 12 weeks after a suspected infection.
  • CDC notes that HSV-1 antibody tests have low sensitivity, so some past infections are missed.
  • Each test brand sets its own index cutoffs and equivocal zone, so check the range printed on your report.

Antibodies take weeks to appear after infection. Herpes is a lifelong infection, and the antibodies generally stay detectable.

When to talk to a clinician

Seek care promptly for painful blisters or sores, especially near the eyes (eye pain, redness, sensitivity to light or blurred vision) or the genitals. Get urgent care for a severe headache with fever and confusion, or if a newborn has blisters, fever or poor feeding.

Questions you could ask

  • Would testing again later change anything for me?
  • What does this result mean for me, given my symptoms or lack of them?
  • If I have a sore, should it be swabbed?

Questions people ask

Does a positive HSV-1 result mean I have genital herpes?

No. HSV-1 is best known for cold sores, and about half of US adults aged 14 to 49 have antibodies. The blood test cannot say whether the infection is in the mouth or the genitals, and CDC says it should not usually be used to diagnose genital HSV-1.

Does a negative result mean I have never had HSV-1?

Usually, but not always. CDC notes that HSV-1 antibody tests have low sensitivity, so some past infections are missed. A test done soon after infection can also be negative because antibodies take weeks to appear.

What does an equivocal result mean?

The index value fell near the lab's cutoff, so the test could not give a clear answer. Your clinician may repeat it later or use a different test.

Show the science and sources

For clinicians and researchers

Type-specific IgG assays use glycoprotein G (gG) to tell HSV-1 from HSV-2, and most report an index value with manufacturer-specific cutoffs for negative, equivocal and positive. CDC (2021) states that HSV-1 serologic testing does not distinguish oral from genital infection, typically should not be performed to diagnose genital HSV-1 infection, and has low sensitivity for detecting HSV-1 antibody. CDC also advises against HSV-2 serologic screening in the general population. NCHS (NHANES 2015 to 2016) found HSV-1 seroprevalence of 47.8% in people aged 14 to 49 (27.0% at ages 14 to 19, 41.3% at 20 to 29, 54.1% at 30 to 39 and 59.7% at 40 to 49), with 50.9% in females and 45.2% in males after age adjustment. IgG results cannot date an infection. This file does not encode index cutoffs because they differ by manufacturer.

LOINC 7909-5 (primary), 17850-9, 5206-8, 51916-5. Specimen: serum.

Sources

  1. Sexually Transmitted Infections Treatment Guidelines, 2021: Genital Herpes, CDC (2021)
  2. Prevalence of Herpes Simplex Virus Type 1 and Type 2 in Persons Aged 14-49: United States, 2015-2016 (NCHS Data Brief No. 304), National Center for Health Statistics, CDC (2018)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

Related markers