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Chlamydia trachomatis is a common sexually transmitted infection that affects men and women. It is caused by a type of bacteria which can go undetected for a very long time and often people have no symptoms. If the infection goes untreated, a person with chlamydia risks health problems.

How it's caught

You can catch chlamydia by having unprotected anal, oral or vaginal sex, or sharing sex toys. So any sexually active person can catch chlamydia, although it is most common in women between the ages of 15 and 19, and men under the age of 25.

It's a very common STI and you or your partner could have picked up the infection from a previous partner without even knowing it. The more sexual partners you have, the more chance you have of being infected.

Chlamydia can also be passed from an infected mother to her baby during childbirth. When this happens, the baby may develop eye or chest infections. Which is why it's important to tell your doctor if you're pregnant and think you have an STI. You can read more about that here.


Most people with chlamydia don’t experience any symptoms, so it is important to get tested if you think you are infected. You can be at risk even if you have had unprotected sex only once.

Symptoms of chlamydia can occur at any time after you have been infected, but they are more likely to show up between one and six weeks after having unprotected sex with someone who has the infection.

Sometimes it's discovered when one partner develops symptoms, but more often it is diagnosed when someone goes for a check-up.

If symptoms are present, these usually include discharge from the penis or vagina, and pain or a burning sensation when peeing.

Women may also experience pain during sex, or bleeding in between periods. Men may notice some discomfort and swelling of the testicles.

If untreated, chlamydia infection can lead to other more serious problems. For example, in women, chlamydia may lead to Pelvic Inflammatory Disease, or fertility problems (difficulty in becoming pregnant).

If men are not treated, the infection may spread to the testicles and cause discomfort. These problems are rare, but the risk increases every time you get chlamydia – so it’s important to get tested.


Testing for chlamydia is simple and done by your GP or a sexual health service for free. Some pharmacies offer chlamydia testing, but they may charge you.

Most people can have the test carried out on a urine sample. Some people have a swab test (a small cotton bud). The swab is used to gently wipe the vagina or penis. Although it is not painful, it may be a little uncomfortable for a moment.

People who have had anal or oral sex might have a swab taken from their rectum or throat. This isn’t done for everyone.

You can also get a chlamydia testing kit you can use at home. Some sexual health services and pharmacies provide free chlamydia testing kits. This involves providing a sample of urine or a swab from the vagina, which you post or take back to the sexual health service for testing. If you use a test kit, remember to follow the instructions carefully. If in doubt, seek advice from a pharmacist, GP or from the sexual health service where you got the kit.

Some testing kits will test for both chlamydia and gonorrhoea.

If you test positive, your pharmacist, doctor or other health adviser will get in touch and tell you what to do next,so it’s important that you include some way of getting in contact with you when you fill in the form with the kit.


Chlamydia infections are easily treated with a course of antibiotics and over 95% of people who are treated will be cured with the first treatment.

Your current and previous partner(s) will be asked to attend for a check-up and to receive treatment.

Sometimes you will be treated straight away, without waiting for the result of a chlamydia test, for example if your partner is known to have an infection or if you have symptoms.

You may be given an antibiotic to take in a single dose, all at once or be given a longer course of treatment, the doctor will discuss this with you.

They'll advise you not to have sex, even with condoms, until 1 week after both you and your partner have finished the treatment and you have no symptoms.

You may be asked to return for another test after your treatment to confirm you have cleared the infection although this isn’t usually needed for uncomplicated chlamydia infection.


The best way to prevent all sexually transmitted infections including chlamydia is to practise safer sex.

This means using a condom for vaginal or anal sex, a a dam or condom for oral sex or practicing safer sex alternatives.


For more information call  0800 22 44 88 or use our sexual health service finder to look for help in your area.