When should I get tested for HIV?
Your situation, your options. A scenario-based guide to HIV testing.
Editorial Standards →Most adults should be tested for HIV at least once, and more often if there's a specific reason. After a possible exposure, the right time to test depends on what happened and when. This page walks through the most common situations — and points you to the right next step, whether that's testing today, testing in 12 weeks, or contacting a clinic urgently. For deeper detail on how HIV tests work, see our guide on the HIV window period .
- Test at home in about 60 seconds.
- Detects HIV-1 and HIV-2 antibodies.
- Discreet, unmarked packaging.
WHO Prequalified
WHO Prequalified for HIV self-testing since 2018.
CE Certified
Self-test certified for the European Union.
FDA Cleared
Cleared by the U.S. Food and Drug Administration.
Health Canada
Approved by Health Canada for over-the-counter self-testing.
Used by clinics and community organisations worldwide.
Find your situation
Choose the situation closest to yours. Each section gives you the right next step and links to deeper information where useful.
I had unprotected sex once with a new or unknown partner
What to do: Plan to test for HIV. The right timing depends on how long ago the exposure was.
- Less than 21 days ago: A self-test won't yet give a reliable result. If you want earlier detection, lab-based 4th-generation tests can detect HIV from around 18 days after exposure1. Otherwise, wait and retest at 21 days.
- 21 days to 12 weeks: An INSTI self-test can detect HIV during this window for most people. A non-reactive result should be confirmed at 12 weeks.
- 12 weeks or more: A self-test result is considered conclusive at this point3.
What else: Consider testing for other STIs at the same time. STIs like chlamydia, gonorrhoea and syphilis are more common than HIV and can be missed if you only test for HIV.
I have unprotected sex regularly or have multiple partners
You're in a higher-risk group, and routine testing is recommended. The CDC, BHIVA and WHO recommend testing every 3 to 6 months for sexually active adults in this group, regardless of symptoms123.
What else to consider:
- PrEP (pre-exposure prophylaxis): a daily medication that reduces the risk of HIV infection from sex by about 99% when taken consistently. Available through sexual health clinics and some online services.
- Routine STI testing: STIs are common in people with multiple partners and most have no symptoms. Regular comprehensive STI screening is the standard recommendation.
Modern self-tests show 100% sensitivity and 99.8% specificity in untrained user studies5 — comparable to rapid tests used in clinics.
I have flu-like symptoms after a possible exposure
Symptoms 2 to 4 weeks after exposure can sometimes be early signs of HIV — fever, sore throat, swollen lymph nodes, rash, fatigue. But: most flu-like illnesses are not HIV, and the symptoms HIV does cause overlap with many common conditions.
What to do depends on how long ago the exposure was:
- Less than 21 days: An antibody self-test is unlikely to give a reliable result yet. If you're concerned, speak to a doctor or clinic about earlier-detection lab tests.
- 21 days or more: Test now. A reactive result needs laboratory confirmation; a non-reactive result should be retested at 12 weeks.
My possible exposure was within the last 72 hours
This is urgent. Post-exposure prophylaxis (PEP) is a 28-day course of medication that can substantially reduce the risk of HIV infection — but it must be started within 72 hours of exposure, and the sooner the better1.
Where to access PEP:
- Sexual health (GUM) clinics — typically able to start PEP same day.
- A&E or emergency departments — out of hours, weekends.
- Some GP services — though referral is sometimes needed.
PEP is not a substitute for testing. After completing the 28-day course, you'll still need to test at 12 weeks after your last dose3.
I'm pregnant or planning pregnancy
HIV testing is part of standard prenatal care across most of Europe4. Every pregnant person is offered an HIV test as part of routine antenatal screening — typically in the first trimester.
Why it matters: if you have HIV, treatment during pregnancy can prevent transmission to your baby almost completely. Without treatment, the risk of mother-to-baby transmission is around 25%; with effective treatment during pregnancy and delivery, that risk drops to less than 1%1.
If you're planning pregnancy and haven't tested recently, now is a good time. Speak to your GP, midwife or sexual health clinic.
I want to test as part of routine sexual health
A self-test gives you a private, accurate result at home. You don't need a specific exposure or reason to take a self-test — many people use it as part of regular sexual health awareness.
The CDC recommends every adult be tested for HIV at least once as part of routine healthcare1. Sexually active adults benefit from testing more frequently, depending on individual circumstances.
If you've never tested before, the easiest first step is to test now. Whatever the result, you have a clear next step.
My partner just tested positive for HIV
First: their result needs laboratory confirmation if it was a self-test. Once confirmed, they should start antiretroviral therapy (ART) as soon as possible. Modern ART is highly effective, and people on treatment with an undetectable viral load cannot transmit HIV to sexual partners (Undetectable = Untransmittable, U=U)6.
For you: get tested. The window period applies — test 21 days after your most recent sexual contact for a screening result, and 12 weeks for a definitive result.
If your most recent contact was within the last 72 hours, contact a clinic about PEP urgently — see Scenario 4 above.
Going forward: PrEP (pre-exposure prophylaxis) may be appropriate for you. If your partner starts effective treatment and reaches an undetectable viral load, U=U applies and onward sexual transmission is prevented.
How HIV testing works
HIV tests detect either antibodies that the body produces against HIV, or the virus itself. Different test types have different windows of reliability — the time between possible exposure and when the test can reliably detect HIV.
Most rapid self-tests, including the INSTI HIV Self Test, detect antibodies. Lab-based 4th-generation tests detect both antibodies and a viral protein called p24, which appears earlier — shortening the window for that test type. Nucleic acid tests (NAT) detect the virus directly and have the shortest window, but they're used in specific clinical situations rather than for routine screening.
Types of HIV tests
- Self-tests (home antibody tests like INSTI): Test at home, result in about 60 seconds, reliable from 21 days, considered conclusive at 12 weeks. 5
- Lab tests (4th-generation antigen/antibody): Reliable from around 18 days, requires a clinic visit and several days for lab results. 1
- NAT (nucleic acid tests): Reliable from around 10 days, used in specific clinical situations, requires a lab.
- Oral fluid self-tests: Generally less sensitive in the early window than blood-based self-tests.
All four test types have high accuracy outside their respective window periods. The INSTI HIV Self Test specifically shows 100% sensitivity and 99.8% specificity in untrained user studies5.
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Order INSTI HIV Self Test →What happens after testing
Non-reactive (negative): the result is reliable from 12 weeks after possible exposure. If you tested earlier, retest at 12 weeks for a definitive result. A non-reactive result at 12 weeks means HIV is not detected.
Reactive (preliminary positive): the result needs confirmation through laboratory testing by a healthcare provider. A reactive self-test is a screening result, not a final diagnosis.
Whatever your result, modern HIV is highly treatable. People diagnosed early have a normal life expectancy, and effective treatment prevents onward sexual transmission (U=U)6.
About the INSTI HIV Self Test
The INSTI HIV Self Test is a CE-certified rapid home test that detects antibodies to HIV-1 and HIV-2 from a single drop of blood. Manufactured by bioLytical Laboratories in Canada, it uses the same testing technology used in clinics — adapted for confidential use at home. Clinical performance data show 100% sensitivity and 99.8% specificity (untrained user study, bioLytical Laboratories)5. Results in about 60 seconds; a reactive result requires confirmatory laboratory testing through a healthcare provider.
Frequently asked questions about HIV testing
How often should I test for HIV?
Do I need a referral or prescription to use a self-test?
Where can I get PEP if I think I've been exposed?
Are home HIV tests as accurate as a lab test?
How do I take an HIV self-test?
How long does it take to get a result?
Choose your kit.
The 2-pack is recommended if you want a backup test or are testing again after the window period.
2 tests
- Test now and again after window period
- Backup if first test is invalid
- Couples or partners testing together
This page is for information only and does not replace medical advice. If you have specific concerns about HIV testing or a possible exposure, contact your doctor or a sexual health clinic. If you are within 72 hours of a possible exposure, do not wait — contact a sexual health clinic or A&E urgently to ask about PEP.