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Chlamydia is often symptom-free, but left untreated can cause serious problems in both men and women. Testing for it is quick and painless and it can be treated with a course of antibiotics.

Chlamydia is caused by bacteria which is found in infected semen and vaginal fluids.

Symptoms of chlamydia:

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 whitish, cloudy or watery discharge
  • pain when urinating.

In the vagina, it can cause:

  • a change in the vaginal discharge
  • pain when urinating
  • pain in the belly or lower back
  • pain during sex
  • 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.

Chlamydia can also be transferred to the eyes, where it can cause conjunctivitis.

How it's passed on

Chlamydia is spread during vaginal, oral or anal sex without condoms. It is also transmitted on sex toys (unless they are washed or covered with a condom each time they are used on a different person).

It is not yet known whether chlamydia is 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 Femidom (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 could make it more likely that you’ll pass on HIV during unprotected sex. But if HIV drugs have made your viral load undetectable then chlamydia or other infections don’t appear to make you more likely to pass on HIV.

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 only take a few seconds and don’t hurt - they may be uncomfortable for a moment or two. Chlamydia is treated with antibiotics. Don’t have sex until treatment has finished or you could pass on the infection. If you were given a single dose of antibiotics you will be asked to wait for a week to have sex.

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.

Next: Genital warts ››

‹‹ Back to: What are STIs?



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The Information Standard: Certified member

This article was last reviewed on 14/9/2015 by Anna Peters

Date due for the next review: 14/9/2018

Content Author: R. Scholey

Current Owner: Health Promotion

More information:

NHS Choices, Combined pill, December 2014

NHS Choices, Is chlamydia only caught through sexual contact?, November 2014

FPA, Chlamydia, July 2014

NHS Choices, Chlamydia - Introduction, June 2015

NHS Choices, Chlamydia - Symptoms, June 2015

NHS Choices, Chlamydia - Getting tested, June 2015

NHS Choices, Chlamydia - Treatment, June 2015

NHS Choices, Chlamydia - Complications, June 2015

Brook, Chlamydia

NHS Choices, Open your eyes to STIs, October 2013

BASHH chlamydia guidelines, BASHH (2006)

Handsfield H, Color Atlas and Synopsis of Sexually Transmitted Diseases (second edition)
McGraw-Hill (2001)

McMillan A, Scott GR, Sexually Transmitted Infections (second edition), Churchill, Livingstone (2000)

British Association for Sexual Health and HIV, UK National Guideline for the Management of Genital Tract Infection with Chlamydia trachomatis, (2006)

Edited by Stephen Morse et al, Atlas of Sexually Transmitted Diseases and AIDS, Third Edition, Mosby (2003)


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The easiest and most effective precaution to take against most STIs is using a condom.