Expert reviewer, Dr Adrian Raby, General Practitioner and Clinical Lecturer
Next review due March 2020

Chlamydia is the most common sexually transmitted infection (STI) in the UK. Most people who get chlamydia are under 25, and it can usually be cured with antibiotics.

Young men and women

Symptoms of chlamydia

You might not get any symptoms of chlamydia – most people don't get any. So you can pass on the infection to somebody you have sex with without even knowing it. If you do get symptoms, you might start to notice them about one to three weeks after you’re infected, although it could be longer.

In women, symptoms to look out for include:

  • an unusual discharge from your vagina – it might look cloudy or be a yellow colour
  • bleeding after you have sex or between your periods
  • pain in the lower part of your tummy (abdomen) or pelvis
  • pain when you wee
  • pain when you have sex

In men, symptoms to look out for include:

  • a milky discharge from your penis
  • pain when you wee
  • swollen, painful testicles

If you have receptive anal sex, you can get a chlamydia infection in your rectum (back passage). Often, you won’t get any symptoms, but you might notice a discharge or blood coming from your anus, and get painful cramps.

If infected semen or vaginal fluid comes into contact with your eyes, you might get conjunctivitis.

If you have any of these symptoms or think you could be at risk, go to a sexual health clinic or contact your GP. Some family planning clinics also provide testing and treatment.

Diagnosis of chlamydia

If you go to see your GP, they may refer you to a sexual health clinic to be tested and to get treatment. You can also make your own appointment and go directly to a sexual health clinic without seeing your GP. All visits are confidential and your details won’t be sent to your GP without your consent.

You can have a test for chlamydia even if you don't have any symptoms. There are different ways to test for the infection, described below.

  • A urine sample. Your clinic or GP might ask you not to go to the toilet for an hour or two before your test.
  • A swab (similar to a small, round cotton bud). Your doctor or nurse will take a sample of cells from your vagina or neck of your womb (in women) or from inside the tip of your penis (in men). If you’ve had anal or oral sex, your doctor or nurse will use a swab to take a sample from your rectum or throat.

Your samples will be sent to a laboratory to be tested and should be available within seven working days. If you already have symptoms of chlamydia, your doctor may offer you treatment without waiting for your test results.

If the tests don’t show that you have chlamydia, but you’ve had unprotected sex recently, you might need to have another test. This should be two weeks after you think you may have caught the infection.

Taking a sample at home

If you’re a woman, it may be possible for you to collect a sample of cells with a swab from your vagina at home. You can then post this, following your health clinic’s instructions. Collecting a sample yourself is sometimes an option for men too – you collect a sample of your urine to send away to be tested.

Telling partners

If the tests show that you have chlamydia, it's important to contact anybody you’ve had sex with. This could be anyone you’ve slept with in the past one to six months, although you might need to go back further. Ask your clinic for advice.

Your past partners may be at risk of having the infection and may need treatment. If they know about this possibility, it will help to prevent them unintentionally spreading the infection to others. Your sexual health clinic may be able to support you with this.

Screening for chlamydia

In England, the National Chlamydia Screening Programme offers free chlamydia tests to men and women under 25. You can have a test every year, or every time you start having sex with someone new. Chlamydia tests are sometimes available at youth clubs, colleges, pharmacies and some GP practices. Depending on where you live, you might be able to order a self-testing kit online that you can post back to a lab to test.

Similar screening programmes run in other parts of the UK. Ask your GP practice or local sexual health clinic if there’s a screening programme in your local area.

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Treatment of chlamydia

It’s usually easy to treat and cure chlamydia. But if you don’t treat it, chlamydia can take a long time to clear up on its own – it can last months or even years.

Your doctor will prescribe you an antibiotic to treat chlamydia. Usually, you’ll either take just one dose of a medicine called azithromycin at the clinic or your GP can prescribe it. Or your doctor might prescribe a course of antibiotics called doxycycline that you’ll need to take for a week.

Once you’re diagnosed with chlamydia, you shouldn’t have sex again until you (and your partner if they are also having treatment) have finished your medication. Ask your doctor when you can get the ‘all clear’ as it varies depending on which type of antibiotic treatment you have.

Causes of chlamydia

Chlamydia is caused by bacteria called Chlamydia trachomatis. These bacteria can infect:

  • in women, the neck of your womb (cervix)
  • your urethra (the tube that carries urine from the bladder and out of your body)
  • your rectum (back passage)
  • your throat (if you have oral sex)
  • your eyes (if you touch your eye with a finger carrying infected fluid from your or your partner’s genitals)

You can get or pass on chlamydia during vaginal, anal or oral sex, as well as by sharing sex toys.

If you’re pregnant, your baby could get an infection when you give birth.

The bacteria can’t survive outside the body for long – certainly no longer than a couple of hours. You don’t get chlamydia from kissing, hugging or sharing baths, towels, cups, plates or cutlery. You also won’t get it from swimming pools or toilet seats.

Complications of chlamydia

If you get treatment for chlamydia early, it’s less likely to cause you further problems. If you don’t get treatment, there’s a risk the infection might spread to other parts of your body and cause complications.

  • In women, chlamydia can lead to pelvic inflammatory disease if the infection spreads to your womb (uterus), fallopian tubes and ovaries. Pelvic inflammatory disease can make you infertile and cause ectopic pregnancy. Chlamydia can also spread to your liver, and cause pain and inflammation (swelling).
  • In men, a chlamydia infection can spread to your testicles, which may lead to pain and inflammation in the tubes that carry sperm. Or it can cause swelling in your prostate gland. Some research has suggested this could be linked with infertility, but doctors don’t know for sure yet.

Chlamydia can cause a reaction in your body that leads to inflammation in the joints in both men and women. This is known as reactive arthritis.

Prevention of chlamydia

There are ways you can lower your risk of getting or passing on chlamydia.

  • Use condoms when you have vaginal, oral or anal sex.
  • Don’t share sex toys. If you do, wash them well or cover them with a new condom before anyone else uses them.
  • Before you have sex with a new partner, you could both consider having a test for chlamydia and other STIs.

Frequently asked questions

  • Tell your doctor or nurse if you’re pregnant or breastfeeding. They’ll choose an antibiotic that’s safest for your baby.

    It’s important to get treatment for chlamydia during your pregnancy. This will reduce your risk of complications, such as your baby being born prematurely. It’s also possible to pass on chlamydia to your baby when you give birth. This can cause conjunctivitis in babies or a lung infection (pneumonia), but there are treatments for both of these conditions.

  • If you think you might have been infected with chlamydia, don’t delay getting tested. The sooner chlamydia is treated, the better your chance of making a full recovery and having fewer complications. You can be tested at a sexual health clinic or GP surgery straight away if you’re worried that you may have it. They might ask you to return a couple of weeks later for a second test to be sure the results are correct.

    You can still have a test even if you don’t have any symptoms. Around half of men, and seven in 10 women will have no symptoms even though they have the infection.

  • You won't usually need to have another chlamydia test after you've finished your treatment. But you might need a follow-up test if:

    • you haven’t taken your antibiotics properly
    • you think you may have been exposed to the infection again
    • you still have symptoms of chlamydia
    • you’re pregnant

    You’ll have this test at least three weeks after you complete your treatment. If you and your partner have had unprotected sex before you both finished your treatments, you might need another test. This is because you might have been infected again with chlamydia.

    If you’re under 25, your clinic might offer you another test for chlamydia three to six months after you finish your treatment.

  • Not usually, because chlamydia often doesn’t cause any symptoms. This means you can have the infection without knowing – you could have had it for months or even years. Depending on how many people you’ve had sex with, it can be hard to trace it to one person. The results of a chlamydia test can’t tell you how long you’ve had chlamydia either.

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Related information

    • 2015 UK national guideline for the management of infection with Chlamydia trachomatis. British Association for Sexual Health and HIV.
    • Opportunistic chlamydia screening of young adults in England: an evidence summary. Public Health England., published April 2014
    • Genital tract chlamydia infection. BMJ Best Practice., last updated 3 October 2016
    • Chlamydia. fpa., published December 2016
    • Find a clinic. fpa., accessed 29 November 2016
    • Sexually transmitted infections in primary care. Royal College of General Practitioners., published 2013
    • Making it work. A guide to whole system commissioning for sexual health, reproductive health and HIV. Public Health England., revised March 2015
    • 2015 BASHH CEG guidance on tests for sexually transmitted infections. British Association for Sexual Health and HIV., amended December 2015
    • Chlamydia trachomatis. UK testing guidelines British Association for Sexual Health and HIV., published 2010
    • Fajardo-Bernal L, Aponte-Gonzalez J, Vigil P, et al. Home-based versus clinic-based specimen collection in the management of Chlamydia trachomatis and Neisseria gonorrhoeae infections. Cochrane Database of Systematic Reviews 2015, Issue 9. doi:10.1002/14651858.CD011317.pub2
    • Chlamydia – uncomplicated genital. NICE Clinical Knowledge Summaries., last revised June 2016
    • Health protection report: infection report. Public Health England., published 5 July 2016
    • Sexual health and contraception. Oxford handbook of general practice (online). Oxford Medicine Online., published April 2014
    • Chlamydia trachomatis. Public Health Agency of Canada., modified 30 April 2012
  • Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, March 2017
    Expert reviewer, Dr Adrian Raby, General Practitioner and Clinical Lecturer
    Next review due March 2020

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