Knowledge Centre
Providing rapid medical guidance and expert health insights for informational purposes. Our guides come from a Harley Street clinic, but they do not replace a professional consultation.
STI symptoms but a negative test? What to do next
Written by Mr Stephen Lingam · Reviewed by Dr Mohammad Bakhtiar (GMC 4694470) on 01/10/2026
Key takeaways
- A negative STI test with ongoing symptoms usually means one of four things: tested too early, the wrong site was sampled, an infection outside the standard panel, or a non-STI cause.
- A GP consultation at Medical Express Clinic is £150; screening packages run from £250 to £665, and the Bronze package (£250) includes the consultation.
- Standard urine and blood testing doesn't automatically include Mycoplasma genitalium (£120.63), Ureaplasma (£120.63), or a throat swab (£104 per site); a doctor's examination decides whether these are worth adding.
- FAST Simple (£350) and FAST Complex (£450) give results in 6 hours; other urine and swab tests take up to 3 working days, and bloods are usually back in 24 hours.
- Non-STI causes, including a urine infection, bacterial vaginosis or thrush, can produce symptoms that look like an STI.
- Reinfection from an untreated partner is worth ruling out if symptoms return after treatment.
A negative test with symptoms that keep going usually comes down to one of four things: it was taken too early, the wrong site was sampled, the infection wasn't on the panel, or the cause isn't a sexually transmitted infection at all. A doctor's examination at our sexual health clinic works out which.
Five reasons symptoms continue after a negative test
Most negative-test-with-symptoms cases fall into a small set of explanations: timing, sample site, a gap in the panel, a non-STI cause, or reinfection. Working out which one applies is what an examination is for.
| Reason | Typical clue | What the doctor does |
|---|---|---|
| Tested too early | Test taken soon after sex, before the infection was detectable | Reviews the timing and advises when to repeat |
| Wrong sample site | Symptoms in the throat or rectum, but only urine was tested | Adds a throat or rectal swab where relevant |
| Infection outside the standard panel | Chlamydia and gonorrhoea are clear but symptoms persist | Considers Mycoplasma genitalium, Ureaplasma, Trichomonas or non-specific urethritis (NGU) |
| A non-STI cause | Symptoms don't fit the usual STI pattern | Examines for a UTI, bacterial vaginosis, thrush or a skin condition |
| Reinfection from an untreated partner | Symptoms return after treatment | Discusses partner testing and retesting |
Infections a standard screen can miss
A standard chlamydia and gonorrhoea test doesn't automatically cover every organism that can cause similar symptoms. Mycoplasma genitalium and Ureaplasma are both tested for at this clinic, at £120.63 each, or £156.25 for the two combined from one sample, and Trichomonas is £120.63.
A throat swab, at £104 per site with results in 2 to 3 days, only happens if it's taken, so symptoms at a site that wasn't sampled won't show up in a urine-only result. Non-specific urethritis (NGU), inflammation without a single organism identified, is another reason symptoms can continue after a clear screen.
Our sister clinic, Sexual Health Clinic London, has more detail on the Mycoplasma genitalium test if you want to read about that infection specifically. At Medical Express Clinic, individual STI tests can be added on their own once a doctor has decided which ones are relevant.
When it isn't an STI
Not every symptom that looks like an STI is one. A urinary tract infection can cause burning or an urge to urinate without discharge; bacterial vaginosis and thrush can cause discharge, odour or itching without being sexually transmitted; and some skin conditions cause soreness or a rash unrelated to infection.
If a urine infection is suspected, the route at this clinic starts with a urine dipstick at the first visit; if that shows anything, the sample can go on for a culture or a full STI screen. Our UTI or STI article covers that distinction in more depth.
What happens at the appointment
A private GP appointment or a sexual health consultation starts with a history and an examination, so the doctor can see what's actually there rather than working from symptoms alone. Which tests get added depends on what that examination suggests, not on repeating the original panel.
For men with discharge specifically, the penile discharge assessment covers examination, testing and treatment together. Extra tests, a throat swab, Mycoplasma genitalium, Ureaplasma or something else, are added only when the history points that way.
Costs
A GP consultation is £150. Sexual health screening packages range from £250 to £665, with the Bronze package (£250) including the consultation. Individual tests start from £68, and a throat swab is £104 per site.
If speed matters, FAST Simple (£350) and FAST Complex (£450) return results in 6 hours. Most other urine and swab tests take up to 3 working days, a throat swab 2 to 3 days, and blood tests are usually back within 24 hours.
Partners and retesting
If an infection is confirmed and treated, an untreated partner can pass it straight back, which looks the same as the original test having been wrong. Your doctor will talk through whether your partner needs testing and when it makes sense to retest, based on which infection was found, if any, and how the treatment was given.
Mr Stephen Lingam
Managing Director
Executive leadership
Frequently asked questions
Can an STI test be wrong?
A test can be negative because it was taken too early, the wrong site was sampled, or the infection isn't one the panel covered, rather than because the test itself was faulty. An examination helps work out which applies.
How long should I wait before retesting?
It depends on which infection is suspected and how recent the exposure was. Our guide to STI window periods sets out the typical timings, and your doctor will confirm the right date for you.
Should I get my throat tested?
Only if there's a reason to, such as oral contact or throat symptoms. A urine or genital swab doesn't cover the throat, so a throat swab (£104 per site, 2 to 3 days) is added separately when it's relevant.
Could it be a UTI?
Yes, a urinary tract infection can cause symptoms that overlap with an STI, particularly burning on urination. The route here starts with a urine dipstick at the first visit, with a culture or full STI screen if that shows anything.
Do I need to see a doctor or just repeat the test?
Seeing a doctor is the more reliable route, since an examination can point to the right test rather than repeating the same panel and getting the same answer.
Should my partner be tested?
If an infection is confirmed, yes, an untreated partner can pass it back. Your doctor will talk through partner testing as part of the same conversation about treatment and retesting.
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