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

You need a test, and you'd like it sorted this week. The local NHS clinic is free but the next appointment is a while off, and a private clinic could see you today. Is the private test actually any better?

On accuracy, no. Both NHS and private clinics use validated tests for the same infections. The real differences are cost, speed and how quickly you can be seen, so the right choice comes down to which of those matters most to you.

If speed is what you're after, our confidential sexual health and GUM clinic at 117a Harley Street sees walk-ins seven days a week, with six-hour results on our FAST packages.

What does NHS sexual health testing offer?

NHS sexual health (GUM) clinics offer free, confidential STI testing and treatment to anyone in England, wherever you live and whether or not 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 area. Some services also offer walk-in sessions or online postal testing, depending on your local NHS trust. If cost is your main concern and you can work around your local clinic's appointments, the NHS is a sound choice.

What does private STI testing add?

Mostly time. You can walk in the same day, choose from a wider range of appointment times, and often get results in hours rather than days. Every screening package here includes a doctor consultation, so you're examined, and if a result needs treating, that's arranged as part of the same visit when it's clinically indicated.

It's also discreet. You can use a pseudonym, and results stay off your NHS record and away from your NHS GP unless you ask us to share them.

How much does private STI testing cost in London?

Individual tests start from £68. Full screening packages range from £250 to £665, with FAST Simple at £350 and FAST Complex at £450. Here are the individual tests people book most, and how long each takes:

For the full list, see specific STI testing.

How fast are results, and when should I test?

It depends on the test. HIV antigen/antibody results can come back 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 sex matters just as much. 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, and under UK guidance a negative result 45 days after exposure is conclusive. If you think you were exposed to HIV in the last 72 hours, go to an NHS sexual health clinic or A&E and ask about PEP straight away, before thinking about a test. For herpes, a swab taken while a blister or sore is present gives a clearer answer than a blood test afterwards.

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

Yes. Urine and blood tests can miss infections in the throat or rectum, so our MSM screening adds throat and rectal swabs. The MSM Full Screen (£550) covers HIV, syphilis, and chlamydia and gonorrhoea at three sites (urine, throat and rectal). The MSM Screen Extended (£1,225) adds a wider swab panel. MSM sexual health screening has the full breakdown.

So which should I choose?

Go to the NHS if cost is your priority and the local appointment times work for you. It's free, and the testing and treatment are reliable. Go private if you want a same-day appointment, a time that suits you, results within hours, or a discreet walk-in setting. Neither is more accurate than the other; you're choosing between access and speed.

What happens at a private sexual health appointment?

Walk in Monday to Friday from 9:00am to 6:00pm or at weekends from 10:00am to 2:00pm, subject to capacity, or book ahead to secure a time. Every screening package includes a doctor consultation and examination. Individual tests can be booked without a consultation when you don't need a clinical assessment.

If you have a specific symptom such as penile discharge, it's assessed and tested in the same visit; see penile discharge assessment. If you'd like same-day testing you can book online, our sister clinic, Sexual Health Clinic London, offers same-day STI testing as a dedicated service.