At-home STI test: when is it accurate, and where can you test free?

Who this is for — and when to go to a clinic today

This guide is for adults without symptoms who want to check after a new partner, a condom that split, or simply because it's been a while. Chlamydia, gonorrhoea and early syphilis often cause no symptoms at all, which is why routine screening exists. The guidelines in the three countries target slightly different groups:

• United States. The US Preventive Services Task Force recommends yearly chlamydia and gonorrhoea screening for sexually active women 24 and under, and for older women at higher risk. The CDC advises everyone aged 13 to 64 to have an HIV test at least once, and yearly if at ongoing risk.
• Canada. The Public Health Agency of Canada now recommends yearly chlamydia and gonorrhoea screening for every sexually active person under 30, and every three to six months for anyone with a new or several partners.
• United Kingdom. The British Association for Sexual Health and HIV advises a test at least yearly and after each new partner, every three months if you're at higher risk. The NHS chlamydia screening programme proactively offers tests to under-25s with a womb or ovaries.

Don't use a kit — get care today if:

• You may have been exposed to HIV in the last 72 hours. Post-exposure prophylaxis (PEP) can stop HIV taking hold, but it must start within 72 hours, and the CDC says every hour counts. Go to a sexual health clinic, urgent care or an emergency department. A test now can't show this exposure; PEP can prevent it.
• You were sexually assaulted. Specialist services offer PEP, emergency contraception, STI care and evidence collection, and you don't have to report to the police. In the US, call the RAINN hotline on 800-656-4673. In the UK, contact a Sexual Assault Referral Centre or the Rape and Sexual Abuse Support Line on 0808 500 2222. In Canada, call 911 or your provincial or territorial support line; our emergency and crisis numbers page lists more.
• You have severe pelvic or lower stomach pain with a fever or vomiting, or sudden, severe pain in a testicle. These need same-day assessment.
• You have symptoms — discharge, a sore or ulcer, pain when urinating, or bleeding after sex. Free postal kits in all three countries are designed for people without symptoms. A clinic can examine you, swab the right place and often treat on the spot.
• You're pregnant. STI tests are part of routine antenatal care; ask your midwife, obstetrician or prenatal clinic rather than buying a kit.

How long to wait after sex

Every STI test has a window period: the time between catching an infection and the test being able to detect it. Test inside the window and a negative result doesn't mean much. That applies equally to a home kit and a clinic test — it's biology, not the kit. The NHS's general advice is that STIs can take up to 7 weeks to show on a test, but the timing differs by infection and by the type of test.

HIV timings from the CDC; UK guidance from BHIVA uses 45 days for a lab test and up to 90 days for self-sampling and self-tests. Syphilis from BASHH: a negative within three months of exposure can't rule it out. Hepatitis B from the CDC (surface antigen appears 6 to 60 days after exposure); hepatitis C from the CDC. Chlamydia, gonorrhoea and syphilis timing as used by NHS sexual health services.

The practical rule NHS sexual health services use: test at two weeks for chlamydia and gonorrhoea, and at about four weeks for HIV and syphilis, then repeat the blood tests at three months if the first round was negative. If you were worried enough to test at one week, that's fine — just plan the repeat.

Two infections are usually left out on purpose. The CDC and BASHH don't recommend herpes blood tests for people without symptoms; the reliable test is a swab of a sore, taken by a clinic. And Mycoplasma genitalium is tested only when there are symptoms or a partner has it, so a "complete" panel that includes it adds cost rather than useful information for most people.

How accurate home kits are, and what they miss

Most home kits aren't really home tests. You collect a sample and post it to the same kind of accredited laboratory a clinic uses, which runs a nucleic acid amplification test (NAAT) for chlamydia, gonorrhoea and trichomoniasis. The CDC says a vaginal swab you take yourself is as accurate as one taken by a clinician, and for men a first-pass urine sample is the preferred specimen. Done at the right time, the lab result is about as reliable as a clinic's.

The weak points are elsewhere:

• The wrong site. Chlamydia and gonorrhoea can infect the throat and rectum after oral or anal sex, and a urine sample won't find them there. The CDC advises testing every site exposed, and BASHH recommends throat, rectal and urine or genital samples for all sexually active gay and bisexual men. Many US kits are urine-only; if yours is, a clinic visit fills the gap.
• Missing infections. Read the panel, not the name. When we checked, neither LetsGetChecked's Standard 5 nor Everlywell's 5-panel kit included HIV. Add a free HIV self-test (see below) or a lab HIV test.
• HIV self-tests. The oral-swab self-test detects about 92% of infections, so roughly 1 in 12 people with HIV gets a false negative, according to the FDA. Any positive self-test needs confirming with a lab test. Finger-prick lab kits are more sensitive but share the 90-day window.
• Instant tests. The first fully at-home test for chlamydia, gonorrhoea and trichomoniasis — a vaginal swab with results in about 30 minutes — was authorised by the FDA in March 2025. In the FDA's data it correctly identified 97% or more of positives. It covers only those three infections and only vaginal samples.

Not sure which tests fit your situation? The at-home test matcher asks about exposure, symptoms and timing, flags anything that needs a clinic instead, and shows the free route for your country first.

Free testing: US, Canada and UK

United States

Under the Affordable Care Act, most plans must cover recommended screening with no cost-sharing in-network: HIV for everyone 15 to 65, syphilis for adults at higher risk, hepatitis C for adults 18 to 79, and chlamydia and gonorrhoea for younger women and women at higher risk. Ask for it to be coded as preventive. Without insurance, the CDC GetTested finder lists confidential clinics near you, many free or low-cost; Title X family planning clinics and Planned Parenthood charge on a sliding scale by income. The CDC-funded Together TakeMeHome programme posts free HIV self-tests anywhere in the US, and some health departments offer free mail-in STI kits by ZIP code. Cash prices for a lab draw ordered online are close to kit prices: Quest charges $105 plus a $6 physician fee for chlamydia and gonorrhoea, and Labcorp OnDemand $59 for syphilis and $99 for HIV.

Canada

Sexual health clinics test free in every province, usually without a referral; Ontario's clinics don't even need a health card, and anonymous HIV testing is available. Several provinces let you skip the waiting room. British Columbia's GetCheckedOnline gives you a lab form after an online questionnaire, for chlamydia, gonorrhoea, syphilis, HIV and hepatitis C, in listed areas. Nova Scotia's STI Care Now posts free kits from age 15, including throat and rectal swabs and an HIV self-test. In Ontario, GetaKit offers free HIV self-tests province-wide and STI kits in participating public health units. Free HIV self-tests are also available nationally to adults through the I'm Ready research programme. Health Canada licensed the first HIV self-test in 2020; CATIE gives its window as three to twelve weeks. We found no major home STI kit company that ships to Canada, so the free routes are the best ones here.

United Kingdom

NHS sexual health clinics are free and confidential. You don't usually need a GP referral, and nothing is shared with your GP unless you ask. STI testing and treatment are free regardless of residency status. Free postal kits for people aged 16 and over without symptoms are available in most areas, through different routes: council-commissioned services in England (enter your postcode on your local sexual health service's site or SH:24), Test and Post from Public Health Wales, SH:24 in Northern Ireland, and local health boards in Scotland. Kits usually cover chlamydia, gonorrhoea, HIV and syphilis, and some services include throat and rectal swabs. Free HIV home tests are available year-round in some council areas through freetesting.hiv, and across England during National HIV Testing Week each February. A paid kit makes sense mainly if you want results faster or want infections the NHS kit doesn't include.

For other free routes — blood tests, a doctor visit, mental-health support — see free care routes in the US, Canada and UK.

Compare your options

Prices checked 20 October 2026 on each provider's site (LetsGetChecked) and can change; sale prices may end. Confirm before buying. For other at-home tests, see compare test kits.

What to do next

1. Check the same-day list above first. A possible HIV exposure in the last 72 hours needs PEP, not a test.
2. Count the days since sex. Two weeks for chlamydia and gonorrhoea; about four weeks for HIV and syphilis, with a repeat at three months if negative.
3. Use the free route if it's open to you: a US preventive visit, public clinic or Together TakeMeHome; a Canadian sexual health clinic or provincial online service; an NHS clinic or free postal kit in the UK.
4. If you buy a kit, match it to the sex you had. After oral or anal sex you need throat or rectal swabs; check the panel includes HIV and syphilis, or add a free HIV self-test.
5. Act on a positive result. Contact a clinic, primary-care clinician, family doctor or GP for treatment, tell recent partners or ask the clinic to, and avoid sex until treatment is finished.

Common questions

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Sources

1. CDC. Getting tested for HIV — window periods by test type. Accessed 9 October 2026.
2. CDC. Post-exposure prophylaxis (PEP). Accessed 9 October 2026.
3. CDC. Sexually Transmitted Infections Treatment Guidelines, 2021 — Chlamydial infections.
4. CDC. Sexually Transmitted Infections Treatment Guidelines, 2021 — Gonococcal infections among adolescents and adults.
5. US Preventive Services Task Force. Chlamydia and gonorrhea: screening (B grade). 2021.
6. US Preventive Services Task Force. Syphilis infection in nonpregnant adolescents and adults: screening (A grade). 2022.
7. HealthCare.gov. Preventive care benefits for adults. Accessed 9 October 2026.
8. US Food and Drug Administration. First test for chlamydia and gonorrhea with home sample collection. 15 November 2023.
9. US Food and Drug Administration. First home test for chlamydia, gonorrhea and trichomoniasis. 28 March 2025.
10. US Food and Drug Administration. Information regarding the OraQuick In-Home HIV Test.
11. British Association for Sexual Health and HIV. UK national guidelines on the management of syphilis. 2024.
12. British HIV Association. HIV testing guidelines — plain-language summary. 2024.
13. British Association for Sexual Health and HIV. Summary guidance on testing for STIs. 2023.
14. Sexual Health Oxfordshire (NHS). When to test after sex. Accessed 9 October 2026.
15. NHS. Sexually transmitted infections (STIs) — sexual health clinics. Accessed 9 October 2026.
16. NHS. HIV and AIDS — diagnosis and post-exposure prophylaxis.
17. Freetesting.hiv. Frequently asked questions — eligibility and areas. Accessed 9 October 2026.
18. Public Health Wales. Free STI testing — Test and Post. Accessed 9 October 2026.
19. UK Health Security Agency. Sexually transmitted infections: migrant health guide — charging exemptions.
20. Public Health Agency of Canada. Recommendations on screening for chlamydia and gonorrhea in non-pregnant adults and adolescents. 2024.
21. Public Health Agency of Canada. STBBI prevention guide — post-exposure prophylaxis.
22. CATIE. HIV testing technologies — window periods. Accessed 9 October 2026.
23. BC Centre for Disease Control. GetCheckedOnline. Accessed 9 October 2026.
24. Nova Scotia Health. STI Care Now. Accessed 9 October 2026.
25. CDC. Recommendations for identification and public health management of persons with chronic hepatitis B. MMWR 2008;57(RR-8).
26. CDC. Viral hepatitis surveillance guidance — markers and timing.
27. CDC. GetTested — find free and low-cost HIV, STI and hepatitis testing. Accessed 9 October 2026.
28. Together TakeMeHome. Free HIV self-tests by mail (CDC-funded). Accessed 9 October 2026.
29. CDC. Sexually Transmitted Infections Treatment Guidelines, 2021 — Genital herpes: screening.
30. CDC. Sexually Transmitted Infections Treatment Guidelines, 2021 — Mycoplasma genitalium.
31. NHS. Help after rape and sexual assault — Sexual Assault Referral Centres.
32. CDC. Intimate partner and sexual violence — resources, including the RAINN hotline.
33. Government of Canada. Gender-based violence — get help now.
34. Government of Ontario. Sexual health clinics. Accessed 9 October 2026.
35. GetaKit (University of Ottawa). Free HIV self-tests and STI kits in Ontario. Accessed 9 October 2026.
36. Quest Diagnostics. Chlamydia and gonorrhea test — price. Accessed 9 October 2026.
37. Labcorp OnDemand. STI tests — prices. Accessed 9 October 2026.
38. LetsGetChecked. At-home STD tests — prices and infections covered. Accessed 9 October 2026.

General information, not medical advice — see our medical disclaimer. Written to the WhereToStart editorial policy. Next scheduled review: 9 April 2027.