Chlamydia is one of the most common sexually transmitted infections (STIs) in the UK. It's passed on through unprotected sex (sex without a condom) and is particularly common in sexually active teenagers and young adults.

If you're a woman, sexually active and under 25 in England, it's recommended that you have a chlamydia test once a year, and when you have sex with new or casual partners.

If you're a man, sexually active and under 25 in England, it's recommended that you have a chlamydia test once a year if you are not using condoms with new or casual partners.

Symptoms of chlamydia

Most people with chlamydia do not notice any symptoms and do not know they have it. If you do develop symptoms, you may experience:

• pain when peeing
• unusual discharge from the vagina, penis or bottom
• in women, pain in the tummy, bleeding after sex and bleeding between periods
• in men, pain and swelling in the testicles

If you think you're at risk of having a sexually transmitted infection (STI) or have any symptoms of chlamydia, visit a GP, community contraceptive service or local genitourinary medicine (GUM) clinic to get tested.

How do you get chlamydia?

Chlamydia is a bacterial infection. The bacteria are usually spread through sex or contact with infected genital fluids (semen or vaginal fluid).

You can get chlamydia through:

• unprotected vaginal, anal or oral sex
• your genitals coming into contact with your partner's genitals – this means you can get chlamydia from someone even if there's no penetration, orgasm or ejaculation

It can also be passed by a pregnant woman to her baby. Chlamydia cannot be passed on through casual contact, such as kissing and hugging, or from sharing baths, towels, swimming pools, toilet seats or cutlery.

Is chlamydia serious?

Although chlamydia does not usually cause any symptoms and can normally be treated with a short course of antibiotics, it can be serious if it's not treated early on.

If left untreated, the infection can spread to other parts of your body and lead to long-term health problems, especially in women.

In women, untreated chlamydia can cause pelvic inflammatory disease (PID), ectopic pregnancy and infertility. In men, in rare cases, chlamydia can spread to the testicles and epididymis (tubes that carry sperm from the testicles), causing them to become painful and swollen. This is known as epididymitis or epididymo-orchitis (inflammation of the testicles).

Getting tested for chlamydia

Testing for chlamydia is done with a urine test or a swab test. You do not always need a physical examination by a nurse or doctor.

Anyone can get a free and confidential chlamydia test at a sexual health clinic, a genitourinary medicine (GUM) clinic or a GP surgery.

In England, if you're a woman under 25 years old, you may be offered a chlamydia test when you visit some health services, for example a pharmacy or GP. This offer is part of the National Chlamydia Screening Programme (NCSP).

If you're a woman, sexually active and under 25 in England, it's recommended that you have a chlamydia test once a year, and when you have sex with new or casual partners.

If you're a man, sexually active and under 25 in England, it's recommended that you have a chlamydia test once a year if you are not using condoms with new or casual partners.

How chlamydia is treated

Chlamydia can usually be treated easily with antibiotics. You may be given a course of doxycycline to take for a week or azithromycin to take once a day for 3 days.

It's important that your current sexual partner and any other recent sexual partners you have had are also tested and treated to help stop the spread of the infection.

Under-25s who have chlamydia should be offered another test 3 to 6 months after being treated. This is because young adults who test positive for chlamydia are at increased risk of catching it again.

Sexual health or genitourinary medicine (GUM) clinics can help you contact your sexual partners.

Preventing chlamydia

Anyone who's sexually active can catch chlamydia. You're most at risk if you have a new sexual partner or do not use a barrier method of contraception, such as a condom, when having sex.

You can help to prevent the spread of chlamydia by:

• using a condom every time you have vaginal or anal sex

If you do share sex toys, wash them or cover them with a new condom between each person who uses them.