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Chlamydia is the most common sexually transmitted infection (STI) in the UK and is most common in under 25s.

Here are some key facts:

  • There are often no signs or symptoms 
  • It can affect anyone who has ever had unprotected sex
  • 1 in 10 young people who are sexually active are thought to have chlamydia
  • It is a bacterial infection 
  • Tests usually involve giving a urine sample or taking a swab
  • If left untreated can affect fertility in men and women
  • It is passed on through unprotected vaginal, anal or oral sex, sharing sex toys or genital-to-genital contact
  • The only way to protect yourself is to use condoms every time you have sex
  • It is treated with antibiotics

You can read about chlamydia in more detail below.

Signs and symptoms of chlamydia

Chlamydia is sometimes described as a ‘silent’ infection due to the fact about 75% of women with chlamydia and 50% of men don’t have any obvious signs or symptoms. 

So even if you don’t have any symptoms, it’s really important you go to be tested for STIs if you’ve had unprotected sex.
You also need to consider emergency contraception if you’ve had unprotected sex. 

If you leave chlamydia untreated it can spread to other parts of the body, causing pain and inflammation. Women are at risk of developing pelvic inflammatory disease (PID) and suffering damage to the fallopian tubes, and men can get an infection in their testicles. In men and women, chlamydia can cause infertility.

If you do have symptoms, they can often take a few weeks to appear and you might notice: 

  • Unusual discharge from the vagina, penis or rectum
  • Burning and itching in the genital area (men)
  • Pain when peeing
  • Heavy periods or bleeding between periods
  • Pelvic and lower abdominal pain
  • Abdominal pain in women during vaginal sex
  • Bleeding during or after sex
  • Painful swelling of testicles

Chlamydia can also infect the rectum or throat if you have unprotected anal or oral sex. If infected semen or vaginal fluid comes into contact with your eyes, this can cause conjunctivitis.

The causes and spread of chlamydia

Chlamydia is caused by bacteria called chlamydia trachomatis that is found in the semen of men and vaginal fluids of women who have the infection. It is passed from one person to another through:

  • Unprotected vaginal sex
  • Unprotected anal sex 
  • Unprotected oral sex 
  • Your genitals coming into contact with your partners genitals
  • Sharing sex toys without washing them or covering them with a condom with each use

Fluid from the penis or vagina can pass chlamydia from one person to another even without penetration, orgasm or ejaculation. It is not clear if chlamydia can be passed on by transferring fluids on the fingers.

You don’t need to have had lots of partners and your partner doesn’t need to have experienced symptoms to pass it on to you.

You cannot get chlamydia from kissing, hugging, sharing baths or towels, swimming pools, toilet seats or from sharing cups, plates or cutlery.

Chlamydia can also be passed from mother to baby during birth but can be treated during pregnancy with antibiotics 

Testing for chlamydia

If you’ve had unprotected sex, don’t wait and hope for the best, have a test as soon as you can. It’s the only way you can be sure that you have chlamydia or not. 

Testing for chlamydia is really simple, painless and doesn’t necessarily require a physical examination by a nurse or doctor.

The test is done with either a urine test or a swab test. The swab looks like a small cotton bud which is wiped over the parts of the body that could be infected. This could be inside the vagina or from the tip of the penis. Very often you can take the swab from inside the vagina yourself. A doctor or nurse may take the swab from the tip of the penis or if you have had oral or anal sex then a swab may be taken from either your throat or rectum. Taking the swab may be  slightly uncomfortable but should not be  painful.

You may be advised to have another test two weeks after having sex. Cervical smear tests and routine blood tests will not detect chlamydia.

Chlamydia testing is free and you can get one at Brook services, other young people's services, GUM or sexual health clinics or at some GP surgeries.

Under 25s can get also get tested for free as part of the National Chlamydia Screening Programme in a range of setting from pharmacies to colleges. You can request a chlamydia test annually or whenever you change your sexual partner.

It is possible to buy chlamydia self-tests to do at home but the accuracy of these tests can vary. Some are very accurate if you carefully follow the instructions. Others are less reliable. Get advice from your nearest Brook clinic, GUM or sexual health clinic, GP or pharmacy if you’re unsure.

Treatment of chlamydia

Chlamydia is treated with a course of antibiotics. The two most commonly prescribed treatments are:

You may be given treatment if you have symptoms which suggest that you could potentially have chlamydia, even if the results of your test have not come back yet.  You will always be offered treatment if your partner is found to have chlamydia.

Most antibiotics are safe to use with hormonal contraception (like the pill, patch, injection or implant) but talk to the person prescribing the treatment to make sure.

Tell the nurse or doctor if you are pregnant or think you may be, or if you are breastfeeding. This will affect the type of antibiotic you are given.

Side effects are usually very mild but may include stomach ache, diarrhoea, feeling sick and thrush.

If you had symptoms, you should notice improvements quite quickly. You should go back to where you had your test if:

  • The symptoms don’t improve within a week
  • You have unprotected sex again
  • You had unprotected sex with your partner before the treatment was finished
  • You did not follow the instructions or complete the treatment
  • The test was negative, but you develop signs and symptoms of chlamydia

You shouldn’t have sex for seven days after your treatment, to prevent you being re-infected or passing the infection on.

It is important that you tell your current and any recent sexual partners that you are being treated for chlamydia, so that they go for treatment too. In the UK it is recommended you tell any sexual partners you have had over the last six months. The staff at Brook or sexual health clinics can help if you find it hard to talk to them about chlamydia.

Some clinics may also offer to contact your partner using what’s called a ‘contact slip’. This is to warn them they may have been exposed and to recommend they get tested and it doesn’t mention your name.

Page last reviewed: May 2015
Next review due: May 2017