Chlamydia is the most common sexually transmitted infection and it’s easily passed on during sex.

It is caused by bacteria that live in warm, moist parts of the body, usually the penis or vagina but sometimes in the throat or rectum.

It’s also found in infected semen and vaginal fluids.


Symptoms might show within one to three weeks of infection, but around half of men and most women have no symptoms.

Chlamydia in the penis can cause a whiteish discharge and a burning feeling, especially when urinating.

It can cause a change in the vaginal discharge, a burning feeling when urinating, pain in the belly or lower back, pain during sex or bleeding between periods or after sex.

Chlamydia in the throat is usually symptom-free.

It usually causes no symptoms in the rectum but might cause discomfort and discharge.

How Chlamydia is transmitted

Chlamydia is spread during vaginal, oral or anal sex without condoms. It can also spread on fingers when you touch an infected part of the body then touch other parts of your or someone else’s body.

Using the male condom or a Femidon (the female condom) cuts the risk. Other types of contraception, such as the contraceptive pill, offer no protection against sexually transmitted infections.

If you have HIV, having untreated chlamydia makes it more likely that you’ll pass on HIV during unprotected sex.

Tests and treatment

There’s a urine test for chlamydia, or a sample can be taken from the infected part of your body using a swab (small cotton bud). Swabs taken from the rectum, throat and vagina don’t hurt – a swab taken from the inside tip of a man’s penis is uncomfortable for a second or two.

Chlamydia is treated with antibiotics. Don’t have sex until treatment has finished or you could pass on the infection. People you have had sex with also need to get checked – a clinic can contact them if you don’t want to. Untreated chlamydia sometimes causes serious problems, including infertility in men and women.

Most people get tested and treated for infections like chlamydia at sexual health (or ‘GUM’) clinics. It is free and confidential – no one else, including your GP will be told about your visit. Some GP surgeries also test for and treat these infections.

The more people you have sex with, especially unprotected sex, the more chance there is of catching infections like chlamydia. You can have them without knowing, so regular check-ups are a good idea, especially if you are starting a new relationship and/or you want to stop using condoms with your partner.

Page content supplied by Copyright 2012 © Terrence Higgins Trust

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