Reviewed by The Wellness Team. Last reviewed October 2026.
Chlamydia is the most common bacterial sexually transmitted infection in the UK, and most people who have it feel completely well. Around 7 in 10 women and half of men with chlamydia have no symptoms at all, which is why testing after unprotected sex matters more than waiting for signs. Testing is a quick urine sample or swab, and treatment is a short course of antibiotics that clears the infection in almost every case.
What chlamydia is
Chlamydia is caused by the bacterium Chlamydia trachomatis. It passes between people through unprotected vaginal, anal or oral sex, and through sharing sex toys that have not been washed or covered with a new condom. It cannot be passed on through kissing, hugging, toilet seats or sharing towels.
Because it is so often silent, chlamydia spreads easily between partners who have no idea either of them carries it. This is why guidelines from NICE and the British Association for Sexual Health and HIV recommend testing after any new partner when a condom was not used, rather than testing only when symptoms appear.
Symptoms in women
When symptoms do appear, they usually show up one to three weeks after exposure and can include:
- A change in vaginal discharge
- Bleeding between periods or after sex
- Pain or burning when passing urine
- Pain during sex
- Lower tummy or pelvic pain
Any of these is worth a same-day conversation with a GP, particularly pelvic pain, which can suggest the infection has spread upwards.
Symptoms in men
In men, chlamydia can cause:
- A white, cloudy or watery discharge from the penis
- Burning or pain when passing urine
- Pain, swelling or heaviness in one or both testicles
Testicular pain needs prompt assessment, because chlamydia can inflame the tubes that store sperm.
Why you cannot rely on symptoms
The single most important fact about chlamydia is that feeling fine proves nothing. Most infections are found by screening, not by symptoms. Left untreated, chlamydia can cause pelvic inflammatory disease in women, which can damage the fallopian tubes and affect fertility, and epididymitis in men. Untreated infection in pregnancy can also be passed to the baby during delivery. All of this is preventable with a simple test and a week of tablets.
How testing works
Testing is straightforward. Men provide a first-catch urine sample. Women can take a vaginal swab themselves, which studies show is as accurate as a clinician-taken swab. The test looks for the bacterium's genetic material and is highly accurate from about two weeks after exposure. Testing earlier than that can miss a new infection, so if a very recent risk is worrying you, a repeat test at the two week mark settles it.
How chlamydia is treated
The first line treatment recommended by national guidelines is doxycycline, one capsule twice a day for seven days. Azithromycin is the usual alternative when doxycycline is not suitable, for example in pregnancy. Three rules make treatment work:
- Take the full course exactly as prescribed.
- No sex at all for seven days after starting treatment, and until any partner has also been treated.
- Partners from the last six months need testing and treatment too, otherwise reinfection is likely.
People under 25 are advised to retest about three months after treatment, because catching it again is common. A test of cure is also recommended in pregnancy.
When to see a GP urgently
Book the same day rather than waiting if you have pelvic or lower tummy pain, pain during sex, a fever with pelvic symptoms, or testicular pain and swelling. These suggest complications that need assessment promptly, not a routine appointment in a fortnight.
What an online GP can do today
A GP can assess your symptoms and risk, arrange confidential testing, prescribe the right antibiotic where treatment is appropriate, and advise on partner notification, all without you visiting a clinic in person. A phone consultation with The Online GP costs £59, a video consultation £150, and an in-person appointment at 10 Portman Square, Marylebone costs £220. Message us on WhatsApp at https://wa.me/447961280835 and we can usually arrange everything the same day.
Frequently asked questions
Can chlamydia go away on its own?
Sometimes the body clears it over many months, but you can pass it on throughout that time and complications can develop silently. Guidelines recommend treating every confirmed infection rather than waiting.
How long after unprotected sex should I test?
Two weeks is the reliable window for the standard test. If you test earlier and the result is negative, repeat at two weeks to be sure.
Is chlamydia serious if I feel fine?
It can be. The damage it causes, particularly to fertility, happens silently. Feeling well is exactly why testing matters.
Do I have to tell my partner?
Yes, partners need testing and treatment or reinfection goes back and forth. If telling them feels impossible, a clinic can contact partners anonymously on your behalf, and we can talk you through both options.
Sources: NICE Clinical Knowledge Summaries, Chlamydia - uncomplicated genital; British Association for Sexual Health and HIV national guideline on the management of Chlamydia trachomatis.
Reviewed by The Wellness Team