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A condom breaking or unprotected sex with a new partner can leave you wanting a test straight away. But testing too early can give a false-negative result, because every STI has a window period: the time between exposure and when a test can reliably pick it up in urine, a swab or blood.
Here’s when each test becomes reliable in Australia, and the one situation where you shouldn’t wait at all.
Medically reviewed by Dr Vafa Derakshan (MBBS, FRACGP). Last reviewed 29 September 2026. Timings checked against the Australian STI Management Guidelines and ASHM HIV testing guidance.
First: could you have been exposed to HIV in the last 72 hours?
If the sex was with someone who has HIV or whose status you don’t know, and especially if it was anal sex without a condom, don’t wait for a test. PEP (post-exposure prophylaxis) must be started within 72 hours, and it works best the sooner it’s started. Speak to a doctor, a sexual health clinic or a hospital emergency department now. Your state’s PEP line, listed on Get PEP, can tell you where to go.
STI window periods at a glance
| Infection | Test | When a test is reliable |
|---|---|---|
| Chlamydia | Urine or swab | About 2 weeks after sex (can show up from about 1 week) |
| Gonorrhoea | Urine or swab | About 2 weeks after sex (can show up from about 1 week) |
| HIV | Laboratory blood test | 6 weeks for a conclusive result. Rapid and self-tests can take up to 12 weeks |
| Syphilis | Blood test | Often from about 6 weeks. After a recent exposure, repeat at 12 weeks |
| Hepatitis B | Blood test | About 6–8 weeks, up to 3 months |
| Hepatitis C | Blood test | About 6–10 weeks, up to 3 months |
| Genital herpes | Swab of a sore | Only when there’s a sore or blister. Blood tests aren’t part of a routine check |
A simple plan after unprotected sex
- Within 72 hours: if HIV is possible, get PEP assessed (above). If pregnancy is possible, emergency contraception from a pharmacy works best the sooner it’s taken.
- At about 2 weeks: test for chlamydia and gonorrhoea. Your doctor may add throat or anal swabs depending on the kind of sex you had.
- At about 6 weeks: blood tests for HIV and syphilis (and hepatitis B or C if relevant).
- At 12 weeks: repeat syphilis (and HIV if you used a rapid or self-test), to be sure.
You don’t need to wait until 6 weeks to book. Many people test at 2 weeks and again at 6 and 12 weeks, and a doctor can set up the right requests in one consult.
What happens if I test too early?
In the first days after an infection, there isn’t enough bacteria, virus or antibody for the lab to detect. A negative result then doesn’t mean you’re clear. It can give false reassurance while an infection with no symptoms is passed on to partners or, for chlamydia and gonorrhoea, causes problems such as pelvic inflammatory disease. If you’ve already tested early, that’s fine: just repeat the test once the window period has passed.
If you have symptoms, don’t wait for the window
Window periods are for people who feel well. If you notice any of these, see a doctor now rather than waiting:
- burning or pain when you pee
- unusual discharge from the penis, vagina or anus
- pelvic, testicular or rectal pain
- sores, blisters, lumps or a rash on the genitals, anus or mouth, or a body rash
- a flu-like illness a few weeks after a possible HIV exposure
A doctor can test from the symptoms (for example, a swab of a sore), and treat sooner when appropriate.
What about Doxy-PEP?
Doxy-PEP is an antibiotic taken after sex (ideally within 24 hours, and no later than 72 hours) to lower the risk of syphilis and chlamydia. Australian guidance supports it for some gay and bisexual men and trans women at higher risk of syphilis, such as those who’ve had syphilis in the last 6 to 12 months. It’s much less effective against gonorrhoea. It isn’t a general “morning-after” option for an STI scare, it doesn’t protect against HIV, and it doesn’t replace testing. A doctor can talk through whether it suits you.
How testing works with STI Doctor
- Book online. An Australian, FRACGP-qualified doctor calls you, usually the same day, 7 days a week.
- Get your pathology request. The doctor chooses the right tests for your timing and sends an electronic request.
- Visit a collection centre. Walk in to any pathology collection centre near you. Standard STI tests are usually bulk billed for Medicare card holders.
- Get your results. You’ll get a text when they’re in, and a follow-up consult. If treatment is needed, an eScript can be sent to your phone.
Consultations are bulk billed for eligible Medicare card holders. Without Medicare, see our fees. Want to know what else can be done quickly? See same-day and rapid STI testing and what a full STI check includes.
Frequently asked questions
How long after unprotected sex can you test for chlamydia and gonorrhoea?
About 2 weeks after sex gives the most reliable result. Tests can sometimes pick them up from about a week, but a negative result before 2 weeks may need repeating.
How soon can an HIV test detect HIV?
A laboratory HIV blood test (antigen/antibody) is conclusive at 6 weeks after exposure. Rapid tests and home self-tests can take up to 12 weeks. If the exposure was in the last 72 hours, ask about PEP now instead of waiting to test.
When should I test for syphilis after unprotected sex?
A syphilis blood test can often detect infection from about 6 weeks. After a recent exposure, guidelines recommend repeating it at 12 weeks.
What happens if I take an STI test too early?
The test may miss an infection that’s there (a false negative). Repeat the test once the window period for that infection has passed.
Is there emergency treatment after an STI exposure?
For HIV, yes: PEP, which must be started within 72 hours. Doxy-PEP can lower the risk of syphilis and chlamydia for some people at higher risk, but it’s not a routine option for a one-off exposure. For most other STIs, the right step is to test at the right time and treat if positive.
Book your STI test
If it’s been 2 weeks or more since unprotected sex, or you have symptoms, book an online STI test. You’ll speak to an Australian doctor by phone or video, 7 days from 9am to 7pm Sydney time, bulk billed for eligible Medicare card holders. If HIV exposure was in the last 72 hours, ask about PEP straight away.
Sources: Australian STI Management Guidelines, standard asymptomatic check-up; Australian STI Management Guidelines, chlamydia; Australian STI Management Guidelines, gonorrhoea; ASHM HIV guidelines (testing and PEP); HIV Self-Testing Australia (3-month window for self-tests); Emen8, STI window periods (Dr Vincent Cornelisse, Melbourne Sexual Health Centre); Ending HIV, testing for HIV and STIs; Get PEP, PEP hotlines; healthdirect, PEP. This article is general information, not personal medical advice.
