How Soon Can You Test for STDs After Exposure? (Window Periods)
Quick answer
The window period is the time between an exposure and the point when a test can reliably detect an infection. For HIV, CDC gives about 10 to 45 days for NAT and lab blood tests, and up to about 90 days for antibody and finger-prick tests. For other STIs, the NHS says infections can take up to 7 weeks to show on a test, so if you have no symptoms it's best to test about 7 weeks after an exposure, or retest then if you tested earlier. If you may have been exposed to HIV in the last 72 hours, do not wait for a test: go to emergency or urgent care now and ask about PEP.
Possible HIV exposure in the last 72 hours? Do not wait to test. Post-exposure prophylaxis (PEP) is a short course of HIV medicine, usually 28 days, and CDC advises starting it as soon as possible and no later than 72 hours after exposure. Go to an emergency department or urgent care clinic and ask for PEP. See HIV PEP: what to do in the first 72 hours.
A window period is the time after an exposure when a test may still come back negative even though an infection is there. It does not mean you are in the clear. Where CDC gives a figure, it is shown below. For infections where CDC gives no single figure, we use the NHS’s cautious guidance: most STIs show on a test within 7 weeks. If in doubt, repeat the test after the window has passed.
What are the window periods for each STD?
| Infection | Test type | Window period |
|---|---|---|
| Chlamydia | NAAT (urine or swab) | Test now if you have symptoms. Without symptoms, test or retest about 7 weeks after exposure (NHS) |
| Gonorrhea | NAAT (urine or swab) | Test now if you have symptoms. Without symptoms, test or retest about 7 weeks after exposure (NHS) |
| Trichomoniasis | NAAT (vaginal swab or urine) | Test now if you have symptoms. Without symptoms, test or retest about 7 weeks after exposure (NHS) |
| Syphilis | Blood test | Up to about 7 weeks (NHS); repeating it later may be advised |
| HIV | Lab antigen/antibody test (blood from a vein) | About 18 to 45 days |
| HIV | Rapid antigen/antibody test (finger-prick blood) | About 18 to 90 days |
| HIV | Antibody test (most rapid and home self-tests) | About 23 to 90 days |
| HIV | NAT (lab test for the virus itself) | About 10 to 33 days |
| Hepatitis B | Blood test | Check the window for the test you order |
| Hepatitis C | Blood test | A negative result may need repeating about 6 months later (NHS) |
| Herpes | Swab of an active sore | Test while a sore is present. A negative swab without a sore does not rule out herpes |
| Herpes | Type-specific blood test (HSV-2) | Repeat about 12 weeks after a possible exposure |
Why does HIV have so many different windows?
Different HIV tests look for different things. CDC describes three types: antibody tests, antigen/antibody tests and nucleic acid tests (NAT). A NAT looks for the virus itself and can detect HIV soonest, so CDC suggests considering it after a recent or possible exposure, especially with early symptoms. Antibody tests, including most rapid and home tests, detect the immune response and take longer to turn positive.
If you had a possible exposure, choose the test that fits your timing. If a test is negative before its window has passed, CDC advises repeating it after the window.
When should I test for chlamydia or gonorrhea?
If you have no symptoms, the NHS advises waiting about 7 weeks after unprotected sex before testing, because STIs can take up to that long to show up. Testing earlier is possible, but a negative result may then need repeating. If you have symptoms such as discharge, burning when you pass urine or pelvic pain, order a test rather than waiting. Chlamydia often causes no symptoms, so a test after a possible exposure can be sensible. CDC advises retesting about 3 months after treatment, whether or not your partners were treated.
What about syphilis, hepatitis and herpes?
For syphilis, the NHS’s 7-week guidance applies, and a repeat test may be advised. For hepatitis C, the NHS says a negative result may need repeating about 6 months later. For hepatitis B, check the window for the test you order. CDC recommends at least one hepatitis C test for adults, and a hepatitis B test at least once for adults, so these are worth doing, and you can order them online.
Herpes is different. If there is a sore, a swab of it is the most sensitive test, and it is best done while the sore is present. Without a sore, CDC says a negative swab does not rule out herpes, and a type-specific blood test may need repeating about 12 weeks after a possible exposure. CDC does not recommend routine herpes blood tests for people without symptoms.
What if my result is negative?
A negative result is reassuring only for exposures older than that test’s window. If your exposure was more recent, or you had new partners since, test again after the window has passed. Until you know your status, using condoms and telling partners that you are waiting on results can help protect everyone.
To order a test online and choose what to include, see which STD test do I need.
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Get care today if
- You may have been exposed to HIV in the last 72 hours. Go to an emergency department or urgent care clinic now and ask for PEP.
- You were sexually assaulted. Seek urgent care promptly and ask about PEP, which CDC guidance covers for victims of sexual assault.
- You develop new symptoms, such as a fever or rash, after a possible HIV exposure. Seek care promptly rather than waiting for a test.
- You have severe pelvic, lower belly or testicular pain.
Call 911 for a medical emergency. Otherwise, urgent care or your doctor can see you today.
When to test
- Within 72 hours of a possible HIV exposureSeek care now and ask about PEP (post-exposure prophylaxis). CDC says to start it as soon as possible, ideally within 24 hours and no later than 72 hours after exposure. A test is not a reason to delay.
- About 10 to 45 days after a possible HIV exposureThis is when NAT (about 10 to 33 days) and lab antigen/antibody blood tests (about 18 to 45 days) can usually detect HIV. When you order an HIV test online, check which type it is so it fits your timing.
- About 90 days after a possible HIV exposureThe longest HIV window for antibody and finger-prick tests. A negative result from an earlier test should be repeated after the window for that test has passed.
- About 12 weeks after a possible herpes exposureA type-specific herpes blood test may need repeating about 12 weeks after the possible exposure. Without a sore, a blood test is the option, and you can order one online.
Common questions
What is a window period?
It is the gap between an exposure and the time a test can reliably show the infection. Testing inside that gap can give a false negative, because there is not yet enough of the germ or antibodies to detect.
If I test negative too early, do I need to test again?
Usually yes. A negative result only counts for exposures older than that test's window period. If you tested early, repeat the test after the full window has passed.
Do I need to wait for symptoms before testing?
No. Chlamydia and many other infections often cause no symptoms, so waiting for symptoms could mean passing an infection on without knowing. Test on the schedule your clinician suggests, and go sooner if symptoms appear.
Can I use a rapid HIV test right after an exposure?
Not reliably. Most rapid and home HIV tests detect antibodies, which take longer to appear. A lab antigen/antibody blood test or a NAT can detect infection sooner.
Sources
- CDC, Getting Tested for HIV (types of HIV tests and window periods)
- CDC, Clinical Guidance for PEP (HIV Nexus)
- CDC, Genital Herpes treatment guidelines (diagnostic considerations)
- NHS, Sexually transmitted infections (STIs)
- NHS, Hepatitis C
- CDC, Chlamydial Infections treatment guidelines (diagnostic considerations and retesting)
This guide is general information written by a patient advocate using public health sources. It is not a diagnosis. Only a clinician who examines you, or a lab test, can tell you what you have. Read how we write and check our guides.