One thing first
If you might have been exposed to HIV in the last 72 hours, don't wait to test. There's medicine that can stop it, and the clock is running. How to get PEP in Ireland.
What a window period is
An infection isn't detectable the moment you get it. There's a stretch of time where you have it but a test can't see it yet. That's the window period.
Test inside it and you can get a negative result that isn't true. The HSE's own guidance for GPs puts it plainly: it's "the time period between when a person comes in contact with a sexually transmitted infection and when a false negative result may occur."
The numbers two Irish sources publish
We're showing you both, side by side, because they don't fully agree — and that difference is the most useful thing on this page.
| Infection | SH:24 Ireland — for its own home kit | HSE guidance for GPs |
|---|---|---|
| Chlamydia | 2 weeks | 2 weeks |
| Gonorrhoea | 2 weeks | 2 weeks |
| HIV | 7 weeks | 45 days |
| Syphilis | 12 weeks | 12 weeks |
| Trichomoniasis | Not published | 4 weeks |
| Hepatitis C | Can take up to 9 months | Not published here |
Neither is wrong. Different tests have different windows, and each source is describing the test it's talking about. SH:24 is describing the kit it posts you; the HSE guidance is describing what a GP or clinic might use.
So the number that matters is the one from whoever is testing you. If you're ordering a home kit, use the kit's timings. If you're going to a clinic, ask them.
If you can't face waiting
You don't have to. SH:24's own advice: "If you're not sure about window periods, you should do a test now, and another test at a later date."
Testing early isn't wasted — it can pick up something from an earlier exposure. It just can't rule out the recent one. So test now if it helps you sleep, and test again when the window has passed.
If you have symptoms, don't wait at all
Window periods are for people with no symptoms who are checking. If something is sore, itching, discharging, or just not right, that's a reason to be seen now — not to count weeks.
The same goes if a partner tells you they've tested positive. Say so when you contact a service; it changes what they do.
Not sure whether what you have counts? Is this an STI or something else?
Timing isn't the only way a test misses things
A test can only find an infection in a place it took a sample from. If you've had oral or anal sex and nobody swabbed your throat or your back passage, waiting longer doesn't help — those sites simply weren't tested.
What we won't tell you
We won't give you a date. We don't know which test you'll be given, and the whole point of the table above is that the answer changes with the test. Anyone who gives you one confident number for "when to test" is glossing over that.
What we will say: book something. A test at a slightly wrong time beats a test you keep putting off.
If you'd rather talk to someone
The HSE runs a freephone sexual health helpline: 1800 700 700. Monday to Friday 8am–8pm, Saturday 9am–5pm. Closed Sundays and bank holidays.
Number and hours per the HSE's sexual health page, checked 10 September 2026.
Where to next
You order directly from SH:24, which runs this service with the HSE. Free if you're 17 or over and live in the Republic of Ireland. Living in Northern Ireland?
Sources and limits
- SH:24 Ireland — When to test (chlamydia and gonorrhoea 2 weeks, HIV 7 weeks, syphilis 12 weeks, hepatitis C up to 9 months; the test-now-and-again advice; the 72-hour HIV warning)
- HSE — Approach to an STI consultation in primary care (definition of a window period; chlamydia and gonorrhoea 2 weeks, trichomoniasis 4 weeks, HIV 45 days, syphilis 12 weeks; follow-up testing should be discussed)
- HSE — Sexual health (free home STI testing eligibility; helpline)
Checked 10 September 2026. This page has not been reviewed by a named clinician and doesn’t claim to have been. It reports what two current Irish sources publish and shows where they differ. It does not tell you which test you need — your provider decides that, and their timing instruction is the one to follow.