Expert reviewer, Dr Adrian Raby, General Practitioner
Next review due August 2022

Chlamydia is the most common sexually transmitted infection (STI) in the UK. It’s more common in people under the age of 25 than in older people but if you’re sexually active, you can get it at any age. Chlamydia is usually easily treated with antibiotics — but the longer you leave it, the more likely it is to lead to complications.

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Causes of chlamydia

Chlamydia is caused by a type of bacteria called Chlamydia trachomatis. The bacteria can infect:

  • your cervix (entrance to your womb) if you’re a woman
  • 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 through having unprotected vaginal, anal or oral sex with an infected person, as well as by sharing sex toys.

If you’re pregnant and have chlamydia, your baby could become infected if they come into contact with the bacteria when you give birth. But this is uncommon.

The bacteria can’t survive outside the body for long. 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.

Symptoms of chlamydia

If you’re a woman, symptoms of chlamydia might include:

  • more discharge than normal from your vagina
  • 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

If you’re a man, symptoms of chlamydia might include:

  • a white, cloudy or watery discharge from your penis
  • pain when you wee
  • swollen, painful testicles

Most women and about half of men with chlamydia either don’t get any symptoms or get symptoms so mild that they don’t notice them. So, you might have the infection — and pass it on to somebody you have sex with — without even knowing it. If you do get symptoms, you might start to notice them from about one to three weeks after you’re infected, although it could be longer.

If you have a chlamydia infection in your rectum (back passage), you might notice some discomfort and discharge from your anus. Although usually, you won’t have any symptoms.

If your eyes are infected (conjunctivitis) you might have some mild irritation, pain and swelling.

If you have any of these symptoms or think you could be at risk, you should arrange to get tested. Find out more about who should get tested and where to go for a test in the section: Diagnosis of chlamydia below.

Diagnosis of chlamydia

The only way to be sure whether or not you have chlamydia is to have a test. If there’s any chance you may have the infection, it’s important to get tested and treated as soon as possible. This will reduce the risk of passing on the infection to anyone else.

Who should have a test for chlamydia?

You should have a test for chlamydia if:

  • you or your partner has any of the symptoms listed in the section above
  • you’ve recently had unprotected sex (sex without a condom) with a new partner
  • your partner has had unprotected sex with another partner
  • a current or recent partner tells you they have a sexually transmitted infection
  • you’ve had two or more sexual partners in the last year
  • you’re pregnant and planning on having an abortion

If you’re under 25 and sexually active, it’s also recommended you have a test for chlamydia:

  • at least once every year or every time you start having sex with someone new
  • if you’ve had treatment for chlamydia in the last three to six months

In England, the National Chlamydia Screening Programme offers free chlamydia tests to all people under the age of 25, as it’s so common in this age group.

Where to get tested

There are a number of services where you can get tested for chlamydia and other STIs. These include genitourinary medicine (GUM) and sexual health clinics, your GP surgery, contraception clinics and some pharmacies. You can also pay to go to a private clinic.

If you see your GP, they may be able to test you at the practice or they may refer you to a GUM or sexual health clinic. You can also make your own appointment and go directly to a GUM or sexual health clinic without seeing your GP. All visits are confidential, and your details won’t be sent to your GP without your consent.

In some areas, sexual health services may provide sample kits that you can use at home and send off to be tested. It’s also possible to buy kits to test yourself at home. However, these aren’t always very accurate, so it’s best to get advice from a pharmacist or doctor.

How is the test for chlamydia done?

There are different ways to test for the infection, described below.

  • If you’re a man, you’ll usually be asked to give a urine sample. Your clinic or GP might ask you not to go to the toilet for an hour or two before your test. Sometimes, your doctor or nurse may also take a sample from the tip of your penis, using a swab (a small round cotton bud).
  • If you’re a woman, you’ll usually need to have a swab from your vagina tested. You may be given a kit to take the swab yourself or your doctor or nurse may take it as part of an examination.
  • If you’ve had anal or oral sex, your doctor or nurse will use a swab to take a sample from your back passage or throat.

Getting your results

Your samples will be sent to a laboratory to be tested and you’ll be told when to expect your results. If you already have symptoms of chlamydia, your doctor may offer you treatment without waiting for your test results.

If your test result is negative but you’ve had unprotected sex in the last two weeks, it’s worth having another test a couple of weeks later.

Telling partners

If the tests show that you have chlamydia, it's important to inform anybody you’ve recently had sex with. This could be anyone you’ve had sex with within the past six months, although your clinic will advise you. They may be at risk of having the infection, so it’s important that they’re tested too. If you’re not already attending a GUM clinic, your GP can refer you to one for support with contacting and informing previous partners.

Treatment of chlamydia

Chlamydia is usually easily treated with antibiotics. Your doctor might prescribe a course of an antibiotic called doxycycline that you’ll need to take for a week. Sometimes, other antibiotics are used instead. For instance, if you’re pregnant, you may be offered treatment with an antibiotic called azithromycin.

If your partner has been diagnosed with chlamydia, you’ll be offered treatment even if you haven’t had your test results back yet.

Once you’re diagnosed with chlamydia, you shouldn’t have sex again until you and your partner have finished treatment. Check with your doctor when exactly this should be, as it can vary depending on which type of antibiotic treatment you have. If you choose to have sex before this point, using a condom will reduce your risk of passing the infection between you and your partner again.

If you take your antibiotic treatment as directed, you should notice an improvement in your symptoms quite quickly. If you delay getting treatment, you risk developing more serious problems, as well as passing the infection to other people. For more information on this, see our section: Complications of chlamydia below.

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, the infection can spread to your womb (uterus), fallopian tubes and ovaries, causing pelvic inflammatory disease. Pelvic inflammatory disease can lead to infertility and can cause ectopic pregnancy.
  • In men, chlamydia can cause pain and swelling in your testicles and in the tubes that carry sperm. This might have an effect on your fertility.
  • Rarely, chlamydia can lead to inflammation in the joints in both men and women. This is known as reactive arthritis.
  • If you get chlamydia when you’re pregnant and you don’t get it treated, it may cause problems with your baby. Your baby may be born too early or with a low birth weight. It’s also possible for your baby to become infected with chlamydia if they come into contact with the bacteria when you give birth. Your baby may develop severe conjunctivitis (infection of the eyes) or infection in their lungs.

Prevention of chlamydia

There are several things you can do to lower your risk of getting or passing on chlamydia, as well as other sexually transmitted infections.

  • Use condoms when you have vaginal, oral or anal sex. You can also use latex squares that cover a woman’s genitals if you’re having oral 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 unprotected sex with a new partner, consider having a test for chlamydia and other STIs.

Frequently asked questions

  • If you think you might have been infected with chlamydia, don’t delay getting checked out. The sooner chlamydia is treated, the easier it is to treat, and the less likely you are to develop complications. You can be tested at a genitourinary medicine (GUM) or sexual health clinic or at your 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 — for instance, you had unprotected sex with your partner before you both finished your treatment
    • 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’re under 25, your clinic should 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

    • Sexually transmitted infections and screening for chlamydia in England, 2018. Health Protection Report. Public Health England, June 2019.
    • Genital tract chlamydia infection. BMJ Best Practice., last reviewed June 2019
    • Nwokolo NC, Dragovic B, Patel S, et al. 2015 UK national guideline for the management of infection with Chlamydia trachomatis. Int J STD AIDS 2016; 27(4): 251–67. doi:10.1177/0956462415615443
    • Chlamydia — uncomplicated genital. NICE Clinical Knowledge Summaries., last revised June 2019
    • Chlamydia. Family Planning Association, December 2016.
    • Update on the treatment of Chlamydia trachomatis (CT) infection. BASHH clinical effectiveness group, September 2018.
  • Reviewed by Pippa Coulter, Freelance Health Editor, August 2019
    Expert reviewer, Dr Adrian Raby, General Practitioner
    Next review due August 2022