Anyone can catch this STI. It is the most common infection in the under 25s.
If left untreated chlamydia can cause serious health problems for men, women and babies.
Testing is straightforward. Chlamydia is easily treated.
What is chlamydia and how is it caught?
Chlamydia is an infection that's usually passed between people during unprotected vaginal, oral or anal sex or when sharing sex toys.
You only need to have unprotected sex once to catch it.
It can be passed from mother to baby during childbirth and cause chest and eye infections in the infant.
How can I avoid catching chlamydia?
If you're going to have sex, always use a condom (or a dam for oral sex with a woman).
How can I tell if I have chlamydia?
You might have a discharge (unusual stuff oozing out) from your penis or vagina and pain or a burning feeling when peeing.
Women may have pain during sex or bleed between periods. Men's testicles (balls) can get swollen and uncomfortable.
Tests are made by giving a urine (pee) sample. Results are usually available within 14 days.
If you have a partner, you should both get tested.
You can get tested by your GP or at your local sexual health service.
Treatment is with antibiotics, usually in a single dose.
You must not have sex even with a condom until 1 week after treatment. Your doctor or nurse will advise you when to come back for a follow up test.