If you are under 25 and sexually active, then you should get tested for chlamydia every year or when you have sex with new or casual partners.
You should also arrange a test if:
You or your partner has symptoms of chlamydia or another STI
You or your partner has had unprotected sex with another person
If you've had sex with someone that you know has chlamydia then you should get tested. You should take the test without delay, however it is important to know that the early stages of this STI do not always show up, so you may need to take another test at a later date to be sure.