The STD test you need depends on what kind of sex you've had and where. Vaginal or oral or anal exposure each points to a urine sample or a self-collected swab at the right site for chlamydia, gonorrhea, and trichomoniasis, plus a blood draw for HIV, syphilis, and hepatitis. This guide maps exposure to the exact test.
| Item | Days after exposure |
|---|---|
| Chlamydia / gonorrhea (NAAT) | ~14 |
| HIV — NAT | 10–33 |
| HIV — antigen/antibody | 18–45 |
| HIV — rapid antibody | 23–90 |
Quick answer: match the exposure to the test
Most STIs come down to two sample types. Chlamydia, gonorrhea, and trichomoniasis are detected with a NAAT — a nucleic acid amplification test — run on a urine cup or a self-collected swab. HIV, syphilis, and hepatitis are blood tests CDC, HIV Testing. The trick isn't picking a fancy panel; it's collecting from the right place. If you've had oral sex, a throat swab catches infections a urine test misses. If you've had receptive anal sex, a rectal swab does the same. A urine-only panel can read negative while an untested site is positive.
Here's the decision tree most clinicians use:
| If you've had… | Test from this site | Plus, by blood |
|---|---|---|
| Vaginal sex (front-hole) | Urine or vaginal swab — NAAT for chlamydia, gonorrhea, trichomoniasis | HIV, syphilis (hepatitis if at risk) |
| Receptive oral sex | Throat swab — NAAT for gonorrhea (and chlamydia) | HIV, syphilis |
| Receptive anal sex | Rectal swab — NAAT for chlamydia and gonorrhea | HIV, syphilis |
| Insertive sex only | Urine — NAAT for chlamydia, gonorrhea | HIV, syphilis |
The essentials: why testing beats how you feel
Many STIs cause no symptoms at all. Chlamydia and gonorrhea are notorious for staying silent — especially in the throat and rectum, and often in the cervix. You can carry and pass an infection while feeling completely fine. Screening catches the infections your body never warned you about. How you feel is not a status test.
This is also why the question isn't just "which test" but "how often." The U.S. Preventive Services Task Force recommends routine chlamydia and gonorrhea screening for sexually active women and others at increased risk, regardless of symptoms USPSTF. If you're not sure of your interval, our guide on how often should you get tested for stds? walks through it by risk profile.
How it works: the science behind each test
A NAAT looks for the genetic material of the bacterium or parasite. Because it amplifies tiny amounts of DNA or RNA, it's the most sensitive method available for chlamydia and gonorrhea, sensitive enough that guidelines have replaced older culture-based methods with it CDC, Chlamydia Treatment Guidelines. Modern NAATs are also highly specific, around 99%, so a positive result is rarely a false alarm. A self-collected vaginal or rectal swab performs as well as a clinician-collected one for these infections, which is why at-home collection is reliable when done correctly.
Blood-based STIs use a different logic. HIV and syphilis testing is built as a two-step process — an initial screening test, then a different confirmatory test — precisely to guard against false positives. A result isn't a diagnosis until the second, confirmatory test agrees with the first. A reactive rapid HIV test, for example, is a preliminary result that must be confirmed with a follow-up lab test before anyone calls it positive CDC, 2024.
The window period — the part people get wrong
There's a gap between exposure and when a test can actually detect an infection. Test inside that gap and you can get a falsely reassuring negative — the test isn't broken, the infection just isn't measurable yet. Testing too early is the single most common cause of a false-negative STD result, and a too-early negative should be repeated.
The windows differ by infection and by test type:
- For chlamydia and gonorrhea, a NAAT is generally reliable about two weeks after exposure. Test sooner and it's reasonable to retest later if a recent exposure is possible.
- For HIV, the window depends on which test you take: a nucleic acid test (NAT) can detect infection roughly 10–33 days after exposure, an antigen/antibody lab test about 18–45 days, and a rapid antibody test about 23–90 days.
- Syphilis antibodies also take time to rise, so an early negative after a known exposure warrants a repeat.
If you're counting days since a specific encounter, our when to test after exposure page lays out the exact timing for each infection so you don't waste a trip on a test that can't yet read true.
Practical details: what testing is actually like
The visit itself is short. For most infections you pee in a cup or do a self-collected swab in a private bathroom; for HIV, syphilis, and hepatitis there's a quick blood draw. It's minutes in the chair, and results usually come back in a day or a few. No part of standard screening requires a pelvic exam unless you have symptoms that call for one.
Access is wider than most people assume. 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 — and at-home and self-collection kits exist for people who'd rather not go in. You're rarely far from a low-cost option: the U.S. has roughly 16,000 federally funded community health centers and about 4,200 Title X family-planning clinics, plus tens of thousands of other public STI clinics HRSA. When you're ready, you can get tested and bring this site map of which samples you need.
One common mistake with at-home kits: people order and swab the day after a scare. Mind the window period and test at the right time, or you'll pay for a result that can't be trusted yet.
What this quiz does not cover
A test-selection guide tells you which sample to collect — it doesn't replace clinical judgment, treatment, or a full sexual-health workup. It won't diagnose herpes from a sore (that needs a lesion sample or specific blood test), it won't tell you whether you need HPV vaccination, and it won't manage a positive result. It also doesn't decide your testing schedule on its own; screening intervals depend on partners, exposures, and risk over time, not on a single quiz.
And it doesn't cover follow-up after a positive. If you test positive for chlamydia, for instance, you'll need treatment and then a retest down the line, because reinfection from an untreated partner is common — see chlamydia reinfection for that step.
When to see a clinician
Pick up the phone — don't wait for a routine cycle — if you have genital sores or ulcers, unusual discharge, pelvic or testicular pain, burning when you pee, or a fever after a possible exposure. See someone promptly too if a partner tells you they tested positive, if a condom broke, or if you may have been exposed to HIV and could be a candidate for post-exposure prophylaxis, which is time-sensitive. A reactive rapid test of any kind always needs in-person confirmation and counseling.