This page is general health information, not medical advice. It cannot tell you whether you have an infection. A clinician can, and the testing options on this site are a good place to start.

You had a sexual encounter, a condom broke, or you just learned a partner was recently diagnosed. Now you are wondering how soon you can test for an STD, and whether a test today would tell you anything.

The answer depends on the infection and the type of test. This guide walks through it step by step. It uses the CDC's published timing and points you to free and low-cost testing in New York City.

What a window period is

A window period is the time between an exposure and the point when a test can reliably detect an infection. A test taken inside that window can come back negative even if an infection is present. That is why timing matters.

A window period is not a sign that something is wrong. It is simply how the body and the lab tests work. Some tests look for the germ itself. Others look for the antibodies or proteins the body makes in response, and those take longer to show up.

Materials you will need

A rough date of the exposure, written down or saved in your phone.
A list of the types of sex involved (vaginal, anal, oral), since this helps a clinician choose which sites to test.
Any current medicines, and your insurance card if you have one. You can still be seen without insurance.
Your questions, written down before the visit.
A few minutes to call or plan a walk-in visit during clinic hours.

Step 1: Note the date and check the 72-hour mark

Start with the date of the exposure. If it was within the last 72 hours, and it involved a possible HIV exposure, act now. The CDC says post-exposure prophylaxis (PEP) is a medicine that may lower the chance of HIV infection, and it must be started within 72 hours. Sooner is better.

PEP is something a clinician prescribes after talking with you. You do not need to wait for a test result to ask about it.

In New York City, the NYC Department of Health and Mental Hygiene lists a 24/7 PEP Hotline at 844-373-7692. The city's sexual health clinics also offer PEP, according to NYC Health.

Step 2: Look up the window period for your situation

The table below covers HIV, where the CDC publishes clear timing by test type. For other infections, the CDC does not publish one fixed window that fits every test, so the table says so plainly.

Infection and test type	When the test can detect it, per CDC
HIV: nucleic acid test (NAT)	About 10 to 33 days after exposure
HIV: antigen/antibody test, blood drawn from a vein	About 18 to 45 days after exposure
HIV: antigen/antibody test, fingerstick	About 18 to 90 days after exposure
HIV: antibody test, including most self-tests	About 23 to 90 days after exposure
Chlamydia, gonorrhea, trichomoniasis	The CDC does not list one fixed window. Ask the clinician how soon to test after your exposure.
Syphilis	The CDC does not list one fixed window for blood tests. Ask the clinician about timing and a possible repeat test.
Herpes and HPV	The CDC does not recommend routine screening of people without symptoms. A clinician can explain what testing is available for your situation.

These ranges are from the CDC's HIV testing guidance and are the same for every gender and sexual orientation. The right test for you depends on your exposure, so a clinician can help you choose.

Step 3: Decide when to test first

The CDC's HIV timing explains why many clinicians suggest two visits. A test early in the range can find some infections. A test later in the range covers more of them.

Here is a simple way to plan:

If you are worried and within the 72-hour PEP period, call or visit a clinic right away.
If it has been longer, you can still test now. A clinician can tell you what a result from today can and cannot tell you.
Ask about a repeat test later, timed to the test type used the first time.

Waiting for an exact day is not required before you ask questions. Clinics can talk through timing with you at any point.

Step 4: Test now, then retest later

Testing now and retesting later are both useful. A first test gives you a starting point and lets a clinician treat anything found. A second test, timed after the window period, checks again for infections that were too new to detect the first time.

The CDC STI Treatment Guidelines (2021) also recommend retesting about three months after treatment for chlamydia, gonorrhea and trichomoniasis. This is because repeat infections are common, often from a partner who was not treated. It is not a judgment about anyone's choices.

Some people have ongoing reasons to test regularly. The CDC recommends that everyone ages 13 to 64 be tested for HIV at least once, and that people with more ongoing chances of exposure test more often. A clinician can help you set a schedule that fits your life.

You can read more about symptoms and when to test in our guide to STD symptoms and when to test. Many infections cause no symptoms at all, so symptoms alone are not a reliable guide to timing.

Step 5: Choose where to test in New York City

You have several free and low-cost choices. For a fuller list, see our guide to STD testing in New York City, or check the local testing list. A few highlights, all from the clinics' own pages:

NYC Sexual Health Clinics (NYC Department of Health and Mental Hygiene). NYC Health describes them as low- to no-cost. Adults 19 and older are asked for insurance or a sliding-scale fee, no proof of income is required, and no one is turned away for inability to pay. Most services are walk-in. Clinics may close early once they reach capacity, so arrive early. Open clinics include Chelsea (303 9th Avenue, Manhattan), Central Harlem (2238 Fifth Avenue), Fort Greene (295 Flatbush Avenue Extension, Brooklyn), Morrisania (1309 Fulton Avenue, Bronx), Jamaica (90-37 Parsons Boulevard, Queens) and Corona (34-33 Junction Boulevard, Queens). Most are open Monday to Friday, 8:30 a.m. to 3:30 p.m. Hours vary at some sites, so confirm before you go. The clinic hotline is 347-396-7959, Monday to Friday, 9 a.m. to 3:30 p.m.
Express clinics. NYC Health lists a Quickie Lab with rapid chlamydia and gonorrhea results at the Chelsea and Fort Greene Express Clinics. At the main Chelsea clinic, NYC Health says to expect results in seven days.
Callen-Lorde Chelsea (356 W 18th St, 212-271-7200). This LGBTQ+ community health center offers STD and HIV testing, PrEP, PEP and doxy-PEP. It says services are available regardless of ability to pay, with a sliding fee for people who are uninsured or underinsured. Saturday walk-in hours run 9 a.m. to 3 p.m., first come, first served. Callen-Lorde also lists sites in the Bronx and Brooklyn.
Mount Sinai Adolescent Health Center (312-320 East 94th Street, 212-423-3000). For young people ages 10 to 26, Mount Sinai says services are completely free, including same-day rapid HIV testing. It lists walk-in hours Monday to Saturday, 8:30 a.m. to 4 p.m.

NYC Health notes that there is no city sexual health clinic on Staten Island in its open list. Crown Heights and Riverside are closed until further notice. If you live on Staten Island, ask the hotline about the closest option.

Free HIV self-test kits

NYC Health says New York City residents can get free HIV self-test kits through Community Home Test Giveaway partner agencies. You can also call 311 or text TESTNYC to 55676. Self-tests are antibody tests, so the table above shows the longer window for them. NYC Health's pages do not list a free at-home kit for other STIs.

Not sure where to go?

The CDC's GetTested locator can help you find testing sites by ZIP code.

Teens and young adults

NYC Health says its Sexual Health Clinics serve anyone 12 or older without parental consent, regardless of immigration status. New York Public Health Law 2305 also lets a licensed physician diagnose and treat a person under 21 for an STD without parental consent. The statute does not mention telling parents.

Step 6: At the visit

Tell the clinician the date and type of exposure. You do not need to explain more than you want to. Clinicians see people of every gender and orientation every day.

Ask these questions:

Which tests are right for my exposure, and which sites should be tested?
What can a result from today tell me, and what can it not tell me?
When should I come back for a repeat test?
Is PEP or another preventive medicine something I should discuss?

If a test finds a bacterial STI or trichomoniasis, the CDC says these are curable with treatment from a clinician. HIV and herpes are not curable, but both are treatable and manageable. HPV is also not curable, though many HPV infections clear on their own.

Under the CDC's 2024 update on doxycycline post-exposure prophylaxis (doxy-PEP), a clinician may discuss it with some people, such as men who have sex with men and transgender women who have had a bacterial STI in the past year. It is prescribed by a clinician, so ask whether it applies to you.

Tips and common mistakes

Testing too early and stopping there. A single early test can miss a new infection. Ask about a repeat test.
Waiting out the PEP window. If a possible HIV exposure was within 72 hours, do not wait for the "right" test date. Call first.
Relying on symptoms. The CDC notes that many STIs cause few or no symptoms.
Mixing up test types. A self-test and a lab blood test have different windows. Know which one you took.
Skipping the retest after treatment. The CDC suggests rechecking about three months after treatment for some infections.
Forgetting partners. Partners may need testing or treatment too. In New York, expedited partner therapy is allowed under Public Health Law 2312, and NYC Health says the CDC recommends it for chlamydia, gonorrhea and trichomoniasis. Ask your clinician how it works.
Having sex before the retest. Using condoms and talking with partners about testing helps protect everyone while you wait.

What results can mean

A test taken after the window period for that test is more likely to give a reliable result. A negative result from a test taken too early may not reflect a recent exposure, which is why a repeat test is often suggested. A clinician can explain what any result means for your situation.

No test is perfect. Results depend on the test type, the timing and the lab. If a result is unclear, a clinician may suggest repeating it.

Why testing matters in New York City

NYC Department of Health and Mental Hygiene's 2024 surveillance report counts 62,774 reported chlamydia cases (760.16 per 100,000) and 32,889 gonorrhea cases (398.27 per 100,000) in the city. NYC Health's HIV report counts 1,791 new HIV diagnoses in 2024. These numbers are a reminder that testing is routine and common here, and there is nothing unusual about asking for it.

NYC Health Code also requires chlamydia, gonorrhea and syphilis to be reported to the Health Department within 24 hours. Reporting is done by clinicians and labs as a public health measure.

Next steps

Write down your exposure date. If it was within 72 hours, call the PEP Hotline at 844-373-7692. If not, choose a clinic above and plan a test now, with a repeat visit timed to the table. Prices and walk-in hours can change, so confirm them with the clinic or the NYC Department of Health and Mental Hygiene before you go.

When to Get Tested After Exposure: STD Window Periods Explained