NHS vs private STI testing in London: what is the difference?

Both NHS sexual health services and private clinics provide accurate STI testing. The main differences are cost, speed and how quickly you can be seen; the right choice depends on which of those matters most to you. Our confidential sexual health and GUM clinic on Harley Street is one private option.

What does NHS sexual health testing offer?

NHS sexual health (GUM) clinics offer free, confidential STI testing and treatment to anyone in England, regardless of where you live or whether you're registered with a GP. Testing is clinically reliable and covers the same core infections a private clinic tests for, including chlamydia, gonorrhoea, HIV and syphilis. Appointment availability and waiting times vary by clinic and by area, and some services also offer walk-in or online postal testing depending on what your local NHS trust provides.

If cost is the main concern, or you are comfortable working around your local clinic's appointment system, the NHS route is a sound choice.

What does private STI testing add?

A private clinic adds speed and flexibility: same-day walk-in appointments, a wider choice of appointment times, and results that are often available in hours rather than days. Every screening package at Medical Express Clinic includes a doctor consultation, so you are examined and, if a result needs treating, that treatment is arranged as part of the same visit when clinically indicated.

Private testing here is also discreet: you can use a pseudonym, and results are not shared with your NHS GP or recorded on your NHS record unless you specifically ask for that.

How much does private STI testing cost in London?

Individual tests start from £68, and full screening packages range from £250 to £665, with FAST Simple at £350 and FAST Complex at £450. The table below shows commonly booked individual tests and how long results take.

For a longer list of individual tests, see specific STI testing.

How fast are results, and does timing after exposure matter?

Results speed depends on the test: HIV antigen/antibody testing can return in 4 to 24 hours, most swab and blood tests in 24 hours to 3 working days, and FAST Simple or FAST Complex packages in 6 hours. Timing after exposure also affects accuracy. Chlamydia and gonorrhoea tests are usually reliable from about 2 weeks after sex. A fourth-generation HIV blood test picks up most infections from 4 weeks after exposure, and under UK guidance a negative result 45 days after exposure is conclusive. If you think you have been exposed to HIV in the last 72 hours, ask an NHS sexual health clinic or A&E about PEP straight away rather than waiting to test. Herpes swab testing is most accurate when a blister or sore is present, which is why a swab taken during an active outbreak gives a clearer answer than a blood test taken afterwards.

Is testing different for men who have sex with men (MSM)?

Yes. Standard urine or blood testing can miss infections at the throat or rectum, so MSM screening at Medical Express Clinic adds throat and rectal swabs to catch these extra-genital infections. The MSM Full Screen (£550) covers HIV, syphilis, and chlamydia and gonorrhoea testing at three sites (urine, throat and rectal); the MSM Screen Extended (£1,225) adds a doctor consultation, examination and a wider swab panel. See MSM sexual health screening for the full breakdown.

When is the NHS the right choice, and when is private testing better?

Choose the NHS route if cost is your priority and you are able to work with local appointment availability; NHS sexual health services are free and provide reliable testing and treatment. Choose private testing if you want a same-day appointment, a specific time slot, results within hours rather than days, or a discreet, walk-in-friendly setting. Neither option is more clinically accurate than the other; the difference is access and speed.

What happens at a private sexual health appointment

Walk-ins are welcome Monday to Friday from 9:00am to 6:00pm and at weekends from 10:00am to 2:00pm, subject to clinic capacity, or you can book ahead to secure a time. Every screening package includes a doctor consultation and examination; individual tests can be booked without a consultation when a clinical assessment isn't needed. If you have a specific symptom such as penile discharge, that is assessed and tested as part of the same visit; see penile discharge assessment for that pathway. If same-day testing with online booking is what you're after, our sister clinic Sexual Health Clinic London offers same-day STI testing as a dedicated service.