How Soon After Sex Should You Test for STDs? Timing, Accuracy & What Londoners Should Know
Marylebone Diagnostic Centre
Results within 24 – 42 hours. Westminster residents receive 20% off.
After unprotected sex or a new partner, many Londoners feel unsure about when to test for sexually transmitted infections (STIs). Testing too early may give a false sense of reassurance, while waiting too long can delay treatment. Clinically, we see this confusion every day at Marylebone Diagnostic Centre. Patients often worry about symptoms, timing, accuracy, and which infections can be detected first.
This guide explains exactly how soon after sex you can test, how long different STDs take to show, and when each test becomes reliable. You will learn the earliest detection windows for chlamydia, gonorrhoea, HIV, syphilis, herpes and other infections, along with early symptoms to watch for. Whether you had unprotected sex, a one-off encounter or a condom break, this information helps you choose the correct timing.
How Quickly Can You Test for STDs After Sex?
The earliest you can test depends on the infection.
Some STIs can be detected in a few days, others take several weeks.
Earliest testing windows:
- Chlamydia: from 7 days
- Gonorrhoea: from 7 days
- Trichomonas: from 7–10 days
- Mycoplasma genitalium: from 7–10 days
- HIV (4th Gen): from 28 days
- Syphilis: from 28 days
- Herpes: only if symptoms appear (swab-based testing)
Testing earlier is still possible, especially if symptoms are present, but a repeat test may be advised.
What Is the Earliest an STD Can Be Detected?
The absolute earliest: 3–5 days
Some infections may show up early in symptomatic cases, but this is not reliable for confirmation.
Most reliable earliest: 7 days
Urine and swab tests for chlamydia and gonorrhoea are most accurate from one week.
Blood-borne infections take longer:
- HIV and syphilis typically require 28 days for reliable detection
- Earlier tests are possible, but may need follow-up
How Long After Sex Should You Get an STI Test?
Recommended testing timeline:
| Infection | Earliest | Most Reliable |
| Chlamydia | 7 days | 14 days |
| Gonorrhoea | 7 days | 14 days |
| Trichomonas | 7–10 days | 14 days |
| Mycoplasma genitalium | 7–10 days | 14 days |
| HIV (4th Gen) | 28 days | 28–45 days |
| Syphilis | 28 days | 6 weeks |
| Herpes | Only with symptoms | Symptom swab |
If exposure was recent, we often test at day 7 and repeat at day 28 for full reassurance.
How Accurate Are STD Tests After 7 Days?
Accurate after 7 days:
- Chlamydia
- Gonorrhoea
- Trichomonas
- Mycoplasma genitalium
- Ureaplasma species
Not fully accurate after 7 days:
- HIV
- Syphilis
- Hepatitis B or C
- Herpes
These require a longer window for reliable detection.
How Long After Unprotected Sex to Test for Pregnancy?
Pregnancy testing is separate from STD testing.
Earliest: 10 days after intercourse
Most reliable: The first day of a missed period
Blood pregnancy testing offers the earliest detection.
How Long Does an STI Take to Show in a Woman?
Women often have silent infections. Symptoms may not appear at all.
If symptoms occur, they appear:
- Within 7–14 days for chlamydia
- Within 3–10 days for gonorrhoea
- Within days to weeks for trichomonas
- Within 2–6 weeks for syphilis (sore or ulcer)
- Within 2–20 days for herpes (only if sores develop)
Most women have no early symptoms, which is why routine testing is essential.
How Long After Unprotected Sex to Get Tested for HIV?
For HIV (4th Generation antigen/antibody test):
- Earliest accurate: 28 days
- More accurate: 28–45 days
- Final confirmation: 90 days
Early “peace-of-mind” testing is sometimes performed at day 14, with follow-up at day 28.
How Long After Sex Should You Test for Herpes?
Herpes testing is only reliable if symptoms appear.
A herpes swab must be taken from:
- A blister
- A sore
- An ulcer
Blood testing cannot confirm a recent infection.
How Long Does It Take for an STD to Show in a Man?
Men may experience symptoms earlier than women, but many infections still remain silent.
Typical onset:
- Gonorrhoea: 2–7 days
- Chlamydia: 7–21 days
- Trichomonas: Often no symptoms
- Syphilis: 2–6 weeks
- Herpes: 2–20 days if sores appear
Testing windows remain the same for both sexes.
Symptoms of STD in Females
Symptoms may include:
- Burning or pain when urinating
- Lower abdominal pain
- Unusual discharge
- Bleeding after sex
- Pelvic discomfort
- Itching or soreness
- Pain during sex
- Genital ulcers or blisters (herpes)
Most women have no symptoms, which is why testing is recommended after any risk.
Early Symptoms of STD in Females
Early signs include:
- Burning after urinating
- Mild pelvic ache
- Light spotting
- Vaginal irritation
- Pain after sex
These can appear before discharge develops.
What Tests Marylebone Diagnostic Centre Offers
Full STD Panel (urine + blood)
Includes:
- Chlamydia
- Gonorrhoea
- Mycoplasma genitalium
- Ureaplasma species
- Trichomonas
- Syphilis
- HIV
Urine Culture & Urinalysis
Useful if burning or pain is present.
Advanced Sexual Health Panel
For extended blood-borne infection screening.
Genital Swabs
If you have symptoms or irritation.
All results are returned confidentially within 24 – 42 hours.
Clinical Notes from MDC
Clinically, we see many patients who test too early, receive a negative result, and assume they are clear.
This can lead to untreated infections.
Testing at the correct window improves accuracy and reduces uncertainty.
If you test at day 7, a follow-up test at day 28 often provides full reassurance.
FAQs
Book a Fast, Private STD Test in London
Marylebone Diagnostic Centre
73 Baker Street, London W1U 6RD
Tel: +44 7495 970109
Open Monday–Saturday, 08:00–16:00
Fast, private, and confidential STD testing with results in 24–42 hours.
Westminster residents receive 20% off all tests.
Quick Links
- Full STI Panel
- Advanced Sexual Health Panel
- Urine Culture & Analysis
- HIV Testing
- Chlamydia & Gonorrhoea Testing
- Syphilis Testing
- Book Your Sexual Health Test
