Chlamydia: Why Testing Matters When There Are No Symptoms
Chlamydia is one of the most commonly reported bacterial sexually transmitted infections in Europe and North America, and the reason it spreads so effectively is simple: most people who have it feel completely well. This is a plain, non-alarmist overview of how it presents, how it is found, how it is treated, and why testing matters more than waiting for symptoms.
How common it is
The World Health Organization estimates there were 128.5 million new chlamydia infections among adults aged 15 to 49 worldwide in 2020, and notes that infection is more common in young people. It is caused by the bacterium Chlamydia trachomatis and passes through vaginal, anal and oral sex, and from mother to baby during birth.
Most cases have no symptoms
The NHS is direct about it: most people who have chlamydia do not have any symptoms. When symptoms do appear, they can start anywhere from a week to several months after infection, and they are usually mild and easy to attribute to something else:
- In women: unusual vaginal discharge, bleeding after sex or between periods, burning when passing urine, pain in the lower abdomen.
- In men: white, cloudy or watery discharge from the penis, burning when passing urine, pain or swelling in the testicles.
- In anyone: pain, bleeding or discharge from the rectum, and occasionally a sore throat or eye redness and discharge.
Because “feeling fine” is the normal presentation, symptoms are a poor guide to who should test. The CDC makes the key point: chlamydia can cause serious health problems even without symptoms.
Why it is worth finding
Untreated, chlamydia can ascend to the upper reproductive tract. In women this can cause pelvic inflammatory disease, which is associated with chronic pelvic pain, ectopic pregnancy and infertility. In men it can cause infection in the testicles, which rarely leads to reduced fertility. The NHS also lists reactive arthritis, joint pain that usually settles after a few months, as a possible complication. WHO adds that infection is associated with a higher risk of acquiring HIV, and in pregnancy with premature birth and eye or lung infections in the newborn.
These outcomes are uncommon relative to the number of infections, but they are largely preventable, and prevention depends on testing rather than waiting for symptoms. The sooner an infection is treated, the less time it has to cause damage.
Testing is straightforward
Diagnosis uses a nucleic acid amplification test (NAAT), which WHO describes as the gold standard. In practice that means a urine sample or a swab, and self-collected swabs perform about as well as those taken by a clinician. Many sexual health services offer free postal kits, and some pharmacies sell them.
If you go to a clinic, the NHS explains what usually happens: a doctor or nurse asks about your symptoms and sexual partners, and you give a urine sample or a swab, which you can often take yourself. You can ask for a chaperone, you can be tested even without symptoms, and you may be offered tests for other infections at the same visit. Nobody needs a reason beyond wanting to know.
Who should test and how often depends on where you live:
| Source | Routine testing advice |
|---|---|
| NHS (England) | Get tested once a year if you are sexually active, and whenever you have a new partner. Free kits are available for under 25s. |
| USPSTF (United States) | Screen sexually active women aged 24 or younger, and older women at increased risk. |
Outside those groups, test after any new partner, if a partner tells you they have an infection, if you have had sex without a condom, or if you are pregnant or planning a pregnancy and think you may have been exposed. Testing for chlamydia is often combined with tests for gonorrhoea, HIV and syphilis.
Treatment
Chlamydia is treated with a short course of antibiotics, usually doxycycline or azithromycin according to CDC treatment guidelines and WHO, and the cure rate is high. Three points do the practical work:
- Finish the course, even if you feel well, and avoid sex until you and any partner have completed treatment and the interval your clinician specifies. WHO advises waiting seven days after taking the medicine.
- Partners need testing and treatment too. Reinfection from an untreated partner is the most common reason people test positive again a few months later. Clinics can notify partners anonymously if that is easier, and in some places clinicians can provide treatment to take to a partner, known as expedited partner therapy.
- Retest if advised. A repeat test a few months after treatment is often recommended, not because the antibiotics failed but because reinfection is common.
Reducing the risk
WHO describes correct and consistent condom use during vaginal and anal sex as the most effective way to prevent chlamydia. There is no vaccine. Regular testing does not prevent infection, but it shortens how long an undetected one persists, which is what most of the harm depends on. Having fewer partners and talking openly about testing with new partners also lower the risk. Our general health section covers routine screening more broadly.
When to see a doctor or sexual health clinic
Get tested promptly if you notice any of the symptoms above, if a current or former partner tells you they have an STI, or if you are pregnant and think you may have been exposed. Seek care urgently if you have pain in the lower abdomen with fever, pain during sex, or sudden pain and swelling in a testicle, as these can signal a complication that needs treatment the same day.
This article is general information, not medical advice. If you think you may have been exposed, contact a sexual health service or your doctor: testing is quick, usually free, and routinely confidential.