Which STI test do I need? How to choose the right test after a new partner

For most people the right test is the Better2Know Peace of Mind screen, taken 14 days after the last time you had sex with your new partner. From a urine sample and a small blood sample it tests for Chlamydia, Gonorrhoea and Syphilis, with results in 2 days, and those three infections are the ones worth ruling out first, because they are common, they often cause no symptoms you would notice, and they are curable with antibiotics once found. Chlamydia and Gonorrhoea were also the two most diagnosed STIs in England in 2025, with 151,163 and 63,943 diagnoses according to UKHSA.

If you would also like HIV and Hepatitis B ruled out, the Full Screen covers all five infections plus Mycoplasma and Ureaplasma, but because HIV and Hepatitis B take longer to become detectable it needs 28 days after the exposure rather than 14. A sensible plan for many people is to do both, taking the Peace of Mind at two weeks and the Full Screen at four.

There are three situations in which the answer changes. If you have symptoms, there is no window period to wait for, and the Comfort Screen tests a single urine sample for seven infections that cause discharge, itching and pain. If you need to know today, our Instant Peace of Mind Screen gives you the result in the clinic in under 30 minutes. And if you want the widest possible check at the two-week point, the Early Platinum Screen adds HIV early detection, Hepatitis B and C, Herpes, Mycoplasma, Ureaplasma, Trichomonas and Gardnerella to the same three infections. The table further down matches each of these situations to its test.

Whichever you choose, the rhythm to keep is the one the British Association for Sexual Health and HIV sets out in its 2023 testing guidance, which is to test at the start of a relationship, then annually and after every change of partner.

Yes, because feeling well tells you very little. Many STIs have no symptoms, as the NHS explains on its STI page, and UKHSA’s National Chlamydia Screening Programme estimates that around 70% to 80% of people with Chlamydia are unaware they have it, while Gonorrhoea, Syphilis and HIV can all go unnoticed for weeks or months. Testing without symptoms is therefore the norm rather than the exception, and UKHSA’s 2025 report shows that 70.3% of the STI tests carried out in England in 2025 were in people without symptoms.

A quiet infection is not a harmless one, either. According to the NHS’s Chlamydia page, untreated Chlamydia can spread to the womb, fallopian tubes and ovaries and cause pelvic inflammatory disease, which can in turn lead to infertility or ectopic pregnancy, and Syphilis and HIV do their damage just as quietly. The reassuring reality is that all of these infections are easy to find with the right test at the right time, and the bacterial ones are cured with antibiotics. Our post “Can I still have an STI if I feel fine?” looks at the silent infections one by one.

That depends on the infection, and the number that matters is the window period, which is the time between catching an infection and the point at which a test can reliably detect it. A test taken before the window closes can still find an infection, so a positive result is accurate, but a negative result is not yet conclusive. Better2Know prints its earliest test day on its product pages as the incubation period, and those are the figures this guide uses.

For Chlamydia, Gonorrhoea and Syphilis that earliest day is 14 days, whether you choose the Peace of Mind or the Instant Peace of Mind Screen, and the Early Platinum Screen also starts at 14 days because it uses PCR technology to find HIV and Hepatitis B and C early. For HIV with the p24 antigen and Hepatitis B on the Full Screen it is 28 days, and if you have symptoms the answer is simply now, with the Comfort Screen, because a positive result is accurate at any point.

Two infections need an extra word. Syphilis antibodies can take longer than 14 days to appear, so if Syphilis is a particular worry BASHH’s 2024 Syphilis guideline advises repeat screening 3 months after any high-risk contact, and if your exposure to HIV was high our HIV page suggests repeating that test 4 to 6 weeks after the first one. If you think you were exposed to HIV in the last 72 hours, seek urgent medical care today, because post-exposure prophylaxis (PEP) can stop the infection taking hold but must be started within 72 hours, as the NHS’s HIV page explains.

General advice often gives a single wait for every STI together, and the NHS’s STI page, for example, suggests 7 weeks if you have no symptoms, because one figure has to cover the slowest infections; this guide gives a date for each test instead. Whichever date applies to you, count it from the last time you were at risk rather than the first. Our guide to the difference between a window period and an incubation period explains why the time to symptoms and the time to a reliable test are not the same thing.

Find your situation in the table below. Every panel, earliest test day, results time and sample is the one shown on the Better2Know product page when we checked on 4 September 2026; results times are working days from your sample reaching the laboratory, and instant results are given in the clinic while you wait.

• A new partner or unprotected sex, no symptoms, 14 days or more ago.
  • Book the Peace of Mind screen that tests for Chlamydia, Gonorrhoea, Syphilis after 14 days incubation.
• You want HIV and Hepatitis B ruled out as well, 28 days or more ago.
  • Book the Full Screen that tests for Chlamydia, Gonorrhoea, Syphilis, HIV and the p24 antigen, Hepatitis B, Mycoplasma, Ureaplasma after 28 days incubation.
• You need the answer today, 14 days or more ago.
  • Book the Instant Peace of Mind screen that tests for Chlamydia, Gonorrhoea, Syphilis after 14 days incubation with same day results.
• You have discharge, itching, pain or a burning feeling when you pee.
  • Book the Comfort Screen that tests for Chlamydia, Gonorrhoea, Mycoplasma, Ureaplasma, Trichomonas, Gardnerella, Herpes after 14 days, or now if you have symptoms.
• You want the widest check possible at two weeks, including HIV.
  • Book the Early Platinum Screen that tests for Chlamydia, Gonorrhoea, Syphilis, HIV (early detection), Hepatitis B, Hepatitis C, Herpes 1 and 2, Mycoplasma, Ureaplasma, Trichomonas, Gardnerella after 14 days.

Two details help you choose well. The first is that a urine sample tests the urethra only, so if you gave oral sex or received anal sex it is worth adding a throat swab or a rectal swab for Chlamydia and Gonorrhoea, which have the same 14-day earliest test day and 2-day results time. BASHH’s 2023 guidance calls for testing at all three sites for men who have sex with men, and an infection in the throat or rectum usually causes no symptoms at all; our post “I had unprotected oral sex. Should I get tested?” explains why oral sex needs testing too. The second is that the earliest test day makes a negative result reliable for most of the panel rather than for every infection on it. Syphilis needs the repeat test described above, and Herpes antibodies take longer still, so our Herpes page advises waiting 4 weeks if you have no symptoms and the Early Platinum Screen’s Herpes result at 14 days is best treated as an early check.

You can test at one of our private clinics across the UK, where many appointments are available the same or next day, or order a home test kit, which arrives in a plain pack, is posted first class the same day for weekday orders placed before 4pm, and comes with a pre-paid return envelope. There is no referral to arrange and no fasting beforehand. Your results go to your secure online patient area, and if anything is found we can arrange a doctor’s consultation and help you with the next steps. Every test is confidential, you can stay anonymous if you prefer, and our Patient Care Team is available 24/7 on 020 7099 0955.

Less happens than you might fear. You book online, by phone or by live chat, choose a clinic and a time, and pay in advance, and at the clinic you give the samples your screen needs, which means a urine sample, a small blood sample and, for some screens, a self-taken swab. A clinician takes you through each one, and most appointments take around 10 to 15 minutes.

Instant screens are run while you wait, with the result in under 30 minutes, while laboratory samples go to an accredited laboratory and the results are reported to your secure online patient area within the times in the table. We notify you by your chosen method when all your results are ready, and you can use a false name or an anonymous PIN if you prefer. Our post “How long do STI test results take?” explains why laboratory results take between 1 and 5 days.

A positive result is the moment the test has done its job, and for most infections what follows is straightforward. Chlamydia, Gonorrhoea and Syphilis are cured with antibiotics, and the NHS notes that Chlamydia treatment may be a single dose or tablets taken for 7 to 14 days. Mycoplasma and Trichomonas are also treated with antibiotics, while our doctors will advise on Ureaplasma, which does not always need treatment. HIV is managed with medication that lets people live long, healthy lives, and most Hepatitis B infections clear on their own, with antiviral medication reserved for the minority that become long-term. If any result is positive, our Sexual Health Advisors contact you and, if you wish, arrange a consultation with one of our doctors in person, by phone or by video, and help you with treatment or a specialist referral.

Two practical points make treatment stick. Avoid sex until you and your partner have both finished treatment, because reinfection is common, and tell your recent partners, since the NHS advises that if you have Chlamydia your current and recent sexual partners need to be tested. It is also worth booking a follow-up test where one is advised; our Gonorrhoea page, for example, recommends a test of cure two weeks after completing treatment.

BASHH’s 2023 summary guidance sets out a simple rhythm. Anyone with one long-term, mutually exclusive partner should test at the start of the relationship, while sexually active people more generally should test annually and after every change of partner, though no more often than every three months. People at higher risk, for example those with many or anonymous partners, should test every three months, and UKHSA’s National Chlamydia Screening Programme adds that sexually active women under 25 should test annually and after a new partner.

In practice that means a Peace of Mind 14 days after each new partner, a Full Screen once a year or when a relationship becomes exclusive and you are thinking of stopping condoms, and a test straight away whenever you have symptoms or a partner tells you they have tested positive. Putting those dates in your phone at the time is far easier than remembering to worry later.

Better2Know’s booking data shows that 44% of sexual health bookings at our UK clinics are for a multi-infection screen rather than a single test. A further 28% are instant tests with results in around 30 minutes, and the remaining 28% are single laboratory tests for one infection.

That split mirrors the advice above, because the same encounter can expose you to several infections at once, and the largest group of people who come to us therefore choose a screen that covers the common ones in a single visit rather than guessing. Instant tests are popular for a related reason, which is that for many people the hardest part of testing is the wait for the result.

Which STI test should I get after unprotected sex?

For most people the right test is the Peace of Mind screen, taken 14 days after the sex you are worried about, which tests for Chlamydia, Gonorrhoea and Syphilis. If you would like HIV and Hepatitis B checked as well, add the Full Screen at 28 days, or book the Full Screen on its own at 28 days if you would rather make a single visit, and if you have symptoms test now with the Comfort Screen.

Do I need an STI test if I have no symptoms?

Yes, you need a test if you have had a new partner or unprotected sex, even with no symptoms, because many STIs cause none, according to the NHS, and around 70% to 80% of people with Chlamydia do not know they have it, according to UKHSA’s National Chlamydia Screening Programme. A test is the only way to know, and UKHSA’s 2025 report shows that 70.3% of the STI tests carried out in England in 2025 were in people without symptoms.

What does a full STI screen test for?

The Better2Know Full Screen tests for Chlamydia, Gonorrhoea, Syphilis, HIV and the p24 antigen, Hepatitis B, Mycoplasma and Ureaplasma from a blood sample and a urine sample taken 28 days or more after the incident you are concerned about, with results in 3 days in clinic or 5 days by home test kit. It is the screen our medical team suggests for a good overall view of your STI status.

Can I do an STI test at home?

Yes, the Peace of Mind and the Full Screen are both available as home test kits, which arrive in a plain pack, are posted first class the same day for orders placed before 4pm on a weekday, and include a pre-paid return envelope. You take a finger-prick blood sample and a urine sample yourself, post them back, and read your results in your secure online patient area, while instant screens remain clinic tests because the result is produced while you wait.

How long do STI test results take?

Peace of Mind results are reported within 2 working days of your sample reaching the laboratory and Full Screen results within 3 days in clinic or 5 days by home test kit, while the Instant Peace of Mind Screen gives a result in the clinic in under 30 minutes. We notify you by your chosen method when all your results are ready, and you read them in your secure online patient area.
Should we both get tested before we stop using condoms?
Yes, you should both test before you stop using condoms, because BASHH advises a test at the start of a relationship and two results replace guesswork. The Full Screen, taken 28 days after each person’s last previous partner, is the screen for that conversation because it includes HIV and Hepatitis B as well as Chlamydia, Gonorrhoea and Syphilis, and testing together, or on the same day, makes it a shared decision rather than an accusation.

Can I test for just one infection?

Yes, Better2Know offers single tests for most of the infections in the screens above, although Chlamydia and Gonorrhoea are usually tested together from one sample, and our Sexual Health Advisors can help you choose the right one if a partner has told you about a specific diagnosis. After a new partner, though, a screen usually makes more sense, because the same encounter can pass on more than one infection and a screen covers the common ones in one visit from one set of samples.

Which STI test you need after a new partner comes down to two questions: what might you have been exposed to, and how long ago? For most people with no symptoms the Peace of Mind at 14 days answers the first worry, and the Full Screen at 28 days adds HIV and Hepatitis B, with a repeat test 4 to 6 weeks later if your exposure was high. Symptoms bring the date forward to today, and an instant screen brings the result forward to the same afternoon.

Testing is the calm, grown-up part of something new, and it takes far less time than the worrying does. Book the Better2Know Peace of Mind at a clinic near you or with a home test kit. Prefer to talk it through first? Our Patient Care Team is available 24/7 on 020 7099 0955.

Medical review. This article was medically reviewed by Dr Steve Chapman. Better2Know content is reviewed for clinical accuracy before publication and updated when guidance or surveillance data changes. It is general information and not a substitute for personal medical advice.

Sources

1. UK Health Security Agency, Sexually transmitted infections and screening for chlamydia in England: 2025 report, 2 June 2026. https://www.gov.uk/government/statistics/sexually-transmitted-infections-stis-annual-data-tables/sexually-transmitted-infections-and-screening-for-chlamydia-in-england-2025-report
2. British Association for Sexual Health and HIV, Summary guidance on testing for sexually transmitted infections, 2023. https://www.bashh.org/_userfiles/pages/files/resources/bashh_summary_guidance_on_stis_testing_2023.pdf
3. NHS, Sexually transmitted infections (STIs), page last reviewed 13 May 2024. https://www.nhs.uk/conditions/sexually-transmitted-infections-stis/
4. NHS, Chlamydia, page last reviewed 24 October 2024. https://www.nhs.uk/conditions/chlamydia/
5. UK Health Security Agency, National Chlamydia Screening Programme: programme overview, updated 24 June 2021. https://www.gov.uk/government/publications/ncsp-programme-overview/ncsp-programme-overview
6. British Association for Sexual Health and HIV, UK guidelines for the management of syphilis, 2024. https://www.bashh.org/_userfiles/pages/files/syphilis_2024.pdf
7. NHS, HIV and AIDS, page last reviewed 9 July 2025. https://www.nhs.uk/conditions/hiv-and-aids/
8. Better2Know UK pages for the Peace of Mind (clinic and home test kit), Full Screen (clinic and home test kit), Instant Peace of Mind Screen, Comfort Screen, Early Platinum Screen, throat and rectal swab tests, the Chlamydia, Gonorrhoea, Syphilis, HIV, Hepatitis B and Herpes information pages, the clinics page and the home tests page, checked 4 September 2026.