Chlamydia test

The type of sample depends on where in your body the infection might be. Most commonly you will either provide a urine sample or take a swab yourself from the vagina. Your doctor or nurse may also take a swab from the cervix (the neck of the womb), throat, or rectum, depending on your symptoms and the type of sex you have had. 

Before your test: 

• if providing a urine sample, try not to urinate for at least one to two hours beforehand — this gives the test the best chance of detecting the bacteria 
• avoid using vaginal douches, creams, or pessaries for 24 hours before a vaginal swab, as these can affect results 
• tell the clinic or your GP if you have recently taken antibiotics, as this may affect the result 

Menstruation does not affect the result. You can be tested during your period if needed. 

What the test measures 

The standard chlamydia test is called a nucleic acid amplification test (NAAT). This test detects the genetic material (DNA or RNA) of the Chlamydia trachomatis bacterium in your sample. NAAT is very accurate — it is both highly sensitive (good at detecting infection when it is present) and highly specific (good at not giving a false positive result). 

The test does not require the bacteria to be alive in your sample. This means it can detect infection even from a self-collected urine sample or vaginal swab, which is why home testing kits can be reliable when used correctly. 

Chlamydia does not cause any changes to blood counts or other routine blood test results. There is no blood test for chlamydia. 

What your results mean 

Negative result (chlamydia not detected) 

No Chlamydia trachomatis DNA was found in your sample. This means you are very unlikely to have chlamydia at this time. However, a negative result is most reliable when: 

• enough time has passed since any potential exposure — the test may miss a very recent infection (within the past week or two) 
• the sample was collected correctly — particularly important for home testing kits 
• you had not recently taken antibiotics before the test 

If you have symptoms, or if you think you may have been exposed very recently, speak to your doctor or sexual health clinic. They may recommend retesting. 

Positive result (chlamydia detected) 

Chlamydia trachomatis DNA was found in your sample. This means you have a chlamydia infection. This is treatable with antibiotics, and most people recover fully with a single course of treatment. 

A positive result does not tell you how long you have had the infection or where you caught it. Chlamydia can be present for months or years without causing symptoms, so a positive result does not necessarily relate to your most recent partner. 

If you receive a positive result, it is important to: 

• start treatment as soon as possible — do not wait for symptoms 
• avoid sexual contact until you and any partners have completed treatment and a short waiting period (usually seven days after treatment) 
• let your recent sexual partners know so they can get tested and treated too

If your result is positive, treatment is straightforward. Chlamydia is treated with a short course of antibiotics — usually azithromycin (a single dose) or doxycycline (taken over a week). Your doctor or sexual health clinic will advise which is more appropriate for you. Both are highly effective. Tell your doctor if you are pregnant, as the choice of antibiotic may differ. 

You should avoid sex — including oral and anal sex — until you and your partner or partners have both completed treatment and waited the recommended period. This is usually seven days after a single-dose treatment, or until the end of a longer course. Your clinic will give you clear guidance. 

A test of cure (repeat test after treatment) is not routinely recommended for most people. However, your doctor may recommend retesting after three months, particularly if you are under 25, pregnant, or at higher risk of reinfection. 

If chlamydia is left untreated, it can lead to serious complications. In women and people with a uterus, it can spread to the womb, fallopian tubes, and ovaries, causing pelvic inflammatory disease (PID). PID can lead to long-term pelvic pain, difficulty getting pregnant, and a higher risk of ectopic pregnancy (a pregnancy outside the womb, which is a medical emergency). In men and people with testes, untreated chlamydia can cause epididymitis (painful inflammation of the tubes near the testes) and, rarely, problems with fertility. Both of these are preventable with early treatment.

• Recent antibiotic use — if you have taken antibiotics in the days before your test, the bacteria may have been partly suppressed, which could cause a false negative result. 
• Incorrect sample collection — self-collected samples need to be done correctly for the test to work well. Postal kits include clear instructions. Ask your clinic if you are unsure. 
• Testing too soon after exposure — it takes time for chlamydia DNA to reach detectable levels. Testing within the first week or so after exposure may give a negative result even if infection is present. If you think you have been exposed very recently, speak to a sexual health service about the right time to test. 
• Vaginal products — douches, creams, or pessaries used shortly before a vaginal swab can affect results. Avoid these for 24 hours before testing. 

Chlamydia is often tested alongside other STIs as part of a full sexual health screen. Your clinic may suggest: 

• Gonorrhoea test — often tested at the same time as chlamydia, as the infections have similar risk factors and sometimes similar symptoms, but require different treatments. 
• HIV test — recommended as part of a routine sexual health screen for anyone who is sexually active. 
• Syphilis test — a blood test, usually included in a full sexual health screen. 
• Hepatitis B and C tests — may be recommended depending on your circumstances. 
• Pelvic examination or ultrasound — if pelvic inflammatory disease (PID) is suspected, your doctor may examine you and may arrange an ultrasound scan to check for complications. 

Chlamydia is a bacterial infection caused by Chlamydia trachomatis. It is passed on through unprotected vaginal, anal, or oral sex, and through sharing sex toys. An infected mother can pass it to her baby during childbirth. It is the most commonly diagnosed STI in the UK, particularly affecting people under 25. It is easily treated, but if left untreated can cause serious reproductive health problems.