When a test can actually find it
Every STI test has a period after exposure where it will come back negative whether or not you have the infection. Here is how long that lasts for each one, and when to book.
Testing three days after a hookup feels like doing something. It mostly is not. Your body has not had time to produce what the test is looking for, so a negative result at that point tells you almost nothing — and people read it as an all-clear and stop thinking about it.
Two terms get mixed up constantly, and the difference is the whole point of this page.
The window period is the time between exposure and when a test can reliably detect the infection. The incubation period is the time between exposure and when symptoms start, if they start at all. They are different numbers, and for most STIs there are no symptoms to wait for. Chlamydia and gonorrhoea are frequently silent, particularly in the throat and rectum.
Testing is not the priority yet. If HIV exposure is possible and you are not on PrEP, PEP has to start within 72 hours and works better the earlier it begins. DoxyPEP, where you have access to it, is also a 72-hour window. Sort that out first, then come back to the schedule below.
The windows, side by side
The lighter end of each bar is when a test may start picking the infection up. The solid end is when a negative result can be treated as conclusive.
The same thing as numbers
| Infection | Test | May detect from | Conclusive at |
|---|---|---|---|
| Chlamydia | NAAT — urine, throat, rectal | 7 days | 14 days |
| Gonorrhoea | NAAT — urine, throat, rectal | 7 days | 14 days |
| HIV | NAT (RNA), venous blood | 10 days | 33 days |
| HIV | Ag/Ab lab test, venous blood | 18 days | 45 days |
| HIV | Ag/Ab rapid, fingerstick | 18 days | 90 days |
| HIV | Antibody only — self-test, oral fluid | 23 days | 90 days |
| Syphilis | Treponemal antibody | 3 weeks | 12 weeks |
| Hepatitis C | Antibody (RNA is faster) | 4 weeks | 12 weeks |
| Hepatitis B | HBsAg | 6 weeks | 12 weeks |
| Herpes | Swab a sore while it is there | Same day | — |
| Mpox | PCR of a lesion | Lesion only | — |
Herpes and mpox sit outside the logic of this page. Both are diagnosed by swabbing something visible, so there is no window to wait out — if you have a sore, that is the moment to get it looked at, not three weeks later. Herpes blood tests exist, take 12 to 16 weeks to become reliable, and are not part of routine screening for good reasons worth their own page.
Chlamydia and gonorrhoea are site-specific. A urine sample finds what is in your urethra and nothing else. If you have had receptive oral or anal sex, throat and rectal swabs are the tests that matter — and rectal infection in particular is usually silent. A urine-only panel comes back clean and misses it entirely.
A schedule that works
You do not need a separate visit per infection. Two rounds cover almost everything.
If you are testing on a routine schedule rather than after a specific incident, this collapses into something simpler: a full panel every three months covers you regardless of what happened in between, which is why that cadence is the standard recommendation for anyone with multiple or anonymous partners.
Questions people actually ask
I bottomed raw at a party on Saturday. When do I test?
Nothing before day 14 will tell you much. If it is still inside 72 hours and you are not on PrEP, the PEP conversation comes first. Then day 14 for chlamydia and gonorrhoea with a rectal swab, and week 12 to close out HIV and syphilis.
I am on PrEP. Do I still need to test after every hookup?
PrEP covers HIV and nothing else. Bacterial infections are unaffected, and rates of them are higher in people on PrEP — not because of the drug, but because of who takes it. The three-month PrEP monitoring visit already includes a full panel, which is one of the underrated benefits of being on it.
I took DoxyPEP. Does that change the timing?
It changes your odds, not the window. If an infection took hold anyway, it is still detectable on the same schedule. Doxycycline taken close to a test can occasionally suppress a bacterial load enough to affect the result, so it is worth mentioning to whoever is doing the testing.
A chemsex weekend, several partners, no clear idea who or when.
Count from the last exposure — that is the clock that matters. Everything before it is already further along. Ask for all three sites and be straightforward about what happened; the panel someone orders depends entirely on what you tell them, and vagueness gets you a urine test.
Negative at four weeks. Am I clear?
For chlamydia and gonorrhoea, yes. For HIV on a lab Ag/Ab test, close but not final — 45 days is the conclusive mark, 90 for a fingerstick or self-test. For syphilis and hepatitis, four weeks is genuinely too early. Re-test at twelve weeks.
Do I have to tell them I have sex with men?
You do not have to explain yourself, but throat and rectal swabs are frequently not offered unless you ask. If saying it out loud is not an option in the room you are in, ask for a three-site screen by name. That phrase gets you the right test without any further conversation.
This page is general information about how tests work, not medical advice, and it cannot tell you whether you have an infection. Window periods are typical ranges — individual results vary, and national guidance differs between countries. Anything specific to your situation is a conversation for a clinician or sexual health service. Candor is a personal record-keeping app; it does not diagnose, treat or prescribe.
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