Understanding Your HSV Testing Options

Getting tested for HSV is one of the most straightforward things you can do for your own clarity — and for the people you care about. There are four main types of HSV tests, and they work quite differently. The right one depends on whether you currently have symptoms and when you think you were first exposed.

You should always work with a medical professional to decide what’s right for your situation. That said, even well-meaning clinicians sometimes default to the wrong test. Use this guide to understand your options and advocate for what you need.

First: What’s a false positive vs. a false negative?

Before diving in, it helps to understand two terms you’ll likely encounter.

• False positive — the test says you have HSV, but you don’t. More common with blood tests, especially at low index values.
• False negative — the test says you don’t have HSV, but you do. More common with swab tests taken too late in the healing process, or blood tests taken too soon after exposure.

Neither outcome means the system is broken. It just means the which and the when really matter — and that’s exactly what this guide covers.

If you have visible symptoms right now

PCR Swab — the gold standard for active symptoms

When you have an active sore, this is the most accurate test available. A clinician swabs the affected area and sends it to a lab, which looks for the virus’s genetic material (DNA). Because PCR can detect even tiny amounts of virus, it’s highly accurate for positive results.

• What it tells you: Whether HSV is present — and which type (HSV-1 or HSV-2)
• Turnaround: Usually 2–5 business days
• Accuracy: A positive PCR result is definitive. [PMC]
• The catch: Timing is everything. The best window is the first 1–3 days of an active sore, when viral concentration is highest. As a lesion heals and crusts over, false negative rates can climb to 25–70%. Get swabbed early if you can.
• Limitation: Requires a visible, active lesion. Not an option if you have no current symptoms.

Viral Culture — older, slower, and largely replaced by PCR

Culture testing works by trying to grow the virus from a swab sample in a lab — a slower, less reliable process than PCR. You may still encounter it, but it’s increasingly rare.

• What it tells you: Whether HSV is actively present. Unlike PCR, standard culture testing cannot distinguish HSV-1 from HSV-2.
• Turnaround: 5–14 days (the lab needs time to grow enough virus to detect)
• The catch: Higher false negative rate than PCR — especially if the lesion is already healing. PCR is preferred whenever available. [NP Women’s Healthcare]

If you don’t have symptoms right now

Blood Test (IgG Antibody Test)

No active sores? A blood test is the go-to. It detects IgG antibodies — proteins your immune system produces in response to HSV. If the antibodies are there, it means your body has encountered the virus at some point in the past.

• What it tells you: Whether you’ve been exposed to HSV
• What it doesn’t tell you: Whether you have an active infection, when or from whom you were first exposed, or which type
• Window period: It typically takes 12–16 weeks after an initial exposure for antibodies to reach detectable levels. Testing too soon can produce a false negative. [Herpes Opportunity]
• Overall accuracy: ~92–95% for HSV-2 and ~91% for HSV-1 — but there’s an important caveat below.

The low-positive zone — this part matters.

If your HSV-2 IgG comes back with an index value between 1.10 and 3.50, hold on before drawing any conclusions. Research shows up to 50% of results in this range are false positives — particularly in lower-risk populations. [UW Medicine | STAT News]

The CDC recommends confirmatory testing for anyone in this range. A result above 3.50 is considerably more likely to be accurate — though your full picture (symptoms, exposure history) still matters.

One more thing: If an IgM test is offered, skip it. The CDC specifically advises against using IgM tests for HSV diagnosis — they’re unreliable and prone to false positives.

Western Blot — the most accurate test that exists

The Western Blot is the gold standard for HSV antibody testing, with over 99% accuracy. It tests for the full range of HSV-specific proteins (not just one, like the IgG test), which makes it far more comprehensive and far less prone to false positives. False positive results on the Western Blot are extremely rare.

It’s the recommended confirmatory test when a blood test result is unclear, low-positive, or doesn’t match your symptoms.

• Accuracy: 99%+
• What it can do that standard blood tests can’t: Definitively distinguish HSV-1 from HSV-2 with much greater confidence
• Results: Usually returned within 1–2 weeks, sometimes longer
• Possible results: Positive, negative, or indeterminate (no numerical index value)

How to get one

The Western Blot is only available through the University of Washington Clinical Virology Lab [testing info packet]. It’s not offered at standard testing sites…which makes getting it done a little complicated. We recommend working with your healthcare provider to complete the test.

1. Request a test kit. Call UW Client Support Services at 206-520-4600 or 800-713-5198, or fill out the kit request form at dlmp.uw.edu. You or your provider can request it.
2. Get your blood drawn. Quest and LabCorp typically won’t draw blood for the Western Blot. Work with your provider to find a suitable lab.
3. Ship the sample to UW. You’ll need a pre-paid UPS or FedEx label to ship the sample directly to the UW lab.
4. Wait for results. Results are delivered to your ordering provider, usually within 1–3 weeks.

Getting a Western Blot done is more involved, more expensive (typically $200+, usually not covered by insurance outside Washington state), and takes longer. But when you need a definitive answer after a low-positive IgG result, it’s the best tool.

What your results actually mean

Positive

A positive result — whether from a swab or a blood test — means HSV was detected. For swab tests, that’s a strong, direct confirmation. For blood tests, it means your immune system has responded to HSV at some point in the past.

What it doesn’t tell you: when you were first exposed, or from whom. HSV can lie dormant for months or even years before any symptoms appear — if they ever do. [ASHA]

A positive result is information. It’s not a verdict. If you’re newly diagnosed, here’s what to know first.

Negative

A negative result means no antibodies (or no active virus) were detected at the time of testing. If you had a potential exposure within the last 12–16 weeks, it’s worth retesting once that window has passed — just to be certain.

Low positive on a blood test

If your HSV-2 IgG index falls between 1.10 and 3.50, don’t jump to any conclusions. Ask your provider about confirmatory testing — a Western Blot can clarify what that number actually means for your situation. [Quest Diagnostics]

Why HSV probably isn’t in your standard STI panel

Most routine screenings test for chlamydia, gonorrhea, syphilis, and HIV. HSV is typically left out — not because it’s unimportant, but because the CDC doesn’t recommend routine asymptomatic screening, given the accuracy nuances of blood tests in lower-risk populations.

What that means for you: a negative STI panel doesn’t tell you your HSV status. If you want to know, ask for it by name. And ask for HSV-1 and HSV-2 to be reported separately — so you have the full picture.

Frequently Asked Questions