A window period is the gap between exposure and when a test can reliably detect an infection. Test too soon and you risk a falsely reassuring negative. For most STIs, a NAAT is dependable about two weeks after exposure; HIV ranges from roughly 10 to 90 days depending on the test type. This chart pairs both the earliest detectable and conclusive timing.
| Item | Days after exposure |
|---|---|
| Chlamydia / gonorrhea (NAAT) | ~14 |
| HIV — NAT | 10–33 |
| HIV — antigen/antibody | 18–45 |
| HIV — rapid antibody | 23–90 |
The essentials: earliest detectable vs. conclusive
There are really two dates you care about after a possible exposure. The first is the earliest a test could pick up an infection — useful if you want answers fast. The second is the conclusive date, when a negative is trustworthy enough to stop worrying. The difference matters because a negative on day three tells you almost nothing; the infection may simply be too new to detect.
Most STIs are tested from a simple sample. Chlamydia, gonorrhea, and trichomoniasis use a nucleic acid amplification test (NAAT) run on a urine cup or a self-collected swab. HIV, syphilis, and hepatitis use a blood draw. None of it takes long, and for many people the hardest part is the timing, not the test itself.
| Infection | Test & sample | Earliest detectable | Conclusive / recommended timing |
|---|---|---|---|
| HIV — NAT (nucleic acid) | Blood draw | ~10 days after exposure | Up to ~33 days |
| HIV — antigen/antibody (lab) | Blood draw | ~18 days | Up to ~45 days |
| HIV — rapid antibody | Finger-stick / oral fluid | ~23 days | Up to ~90 days |
| Chlamydia | NAAT — urine or swab | Around 2 weeks | Retest later if tested sooner |
| Gonorrhea | NAAT — urine or swab | Around 2 weeks | Retest later if tested sooner |
| Trichomoniasis | NAAT — urine or swab | Around 2 weeks | Retest if exposure was recent |
| Syphilis | Blood draw (two-step) | Weeks after exposure | Confirm with second test before final |
One thing the chart can't replace: many STIs cause no symptoms at all. How you feel doesn't tell you your status — testing does. Screening is how silent infections get caught, which is why the timing of a test, not the presence of a sore or discharge, drives the schedule. If you want a deeper walkthrough of timing for your specific situation, see when to test after exposure.
How window periods actually work
A test doesn't detect "infection" in the abstract — it detects something measurable: the pathogen's genetic material, a viral protein, or the antibodies your immune system makes in response. Each of those appears on its own schedule, which is why the same infection can have several window periods depending on which test you use.
NAATs: detecting the organism's DNA or RNA
A NAAT amplifies tiny amounts of a pathogen's nucleic acid until there's enough to measure. Because it's looking for the organism directly rather than your immune response, it turns positive relatively early. For chlamydia and gonorrhea, a NAAT is generally reliable about two weeks after exposure USPSTF. NAATs are also the most sensitive method available — modern versions have specificity around 99%, meaning false positives are rare CDC. That accuracy is exactly why they're the recommended test.
HIV: why three different windows exist
HIV illustrates the principle best. A nucleic acid test (NAT) hunts for viral RNA and can detect infection roughly 10 to 33 days after exposure. An antigen/antibody lab test looks for both a viral protein and antibodies, picking up infection about 18 to 45 days out. A rapid antibody test detects only antibodies, which take longest to build, so its window runs about 23 to 90 days CDC, HIV Testing. Earlier detection isn't always better — the right test depends on how recent the exposure was and how soon you need an answer.
Syphilis: a two-step process
Syphilis testing uses two different tests to confirm a result, because a single screen can occasionally react when no infection is present. The lab runs an initial screening test, then a separate confirmatory test, and the result isn't final until both agree CDC, 2024. This two-step approach guards against false positives — a real concern with a diagnosis this consequential. HIV diagnosis works the same way: a reactive rapid HIV result is preliminary and must be confirmed by a follow-up lab test before it counts as a diagnosis.
Practical details: timing your test right
The single most common cause of a false negative is testing before the window period is over. The test isn't malfunctioning — the infection just isn't detectable yet. A too-early negative should always be repeated once enough time has passed. If a recent exposure is possible and you tested early for chlamydia or gonorrhea, retesting later is reasonable rather than optional.
Here's what testing actually looks like in practice:
- You'll either pee in a cup or swab yourself for most infections, and have a quick blood draw for HIV, syphilis, and hepatitis — a few minutes in the chair total.
- Results typically come back in a day or a few, depending on the test and the clinic.
- At-home and self-collection kits exist and work well — just mind the window period so you collect your sample at the right time, not the day after exposure.
- If you're outside the window, it's worth waiting a few days rather than paying for a test that can't yet give you a real answer.
Cost is rarely the barrier people fear. Testing is available at doctors' offices, health departments, Planned Parenthood, and Title X family-planning clinics — often free or on an income-based sliding scale. The US has roughly 16,000 federally-funded community health centers and about 4,200 Title X clinics, plus tens of thousands of other public STI clinics HRSA. You're rarely far from low-cost care. To find a spot, see where can i get tested for stds? or go straight to get tested.
What this chart does not cover
Window periods tell you when to test — not how often, and not what to do with a positive. Screening intervals depend on your age, sexual activity, and risk factors, and they're a separate conversation from a single post-exposure test. This chart also doesn't replace treatment guidance or follow-up testing.
One important gap: a clear test today doesn't protect you from getting reinfected tomorrow. After treatment for chlamydia, for example, a follow-up test weeks later catches reinfection — a different question from the window period. If that applies to you, read about chlamydia reinfection. The numbers in this chart also assume a one-time exposure; ongoing exposure resets your clock each time.
When to see a clinician
Get evaluated promptly — don't wait out a window — if you have symptoms like discharge, burning with urination, sores, unusual bleeding, or pelvic pain. Symptoms warrant a visit even if you're inside the window, because a clinician can examine you, swab the right site, and treat presumptively if needed. Also see someone if a partner tests positive, if a rapid test was reactive (so it can be confirmed), or if you've had a known high-risk exposure and want to discuss prevention options. When in doubt about timing, a clinician can tell you exactly when your test will be conclusive.