If you are sexually active should take a chlamydia test annually and another chlamydia test every time you change partner, according to the Health Protection Agency.
You should always use a condom with a new partner until both of you have taken a chlamydia test that is clear.
The HPA has just published figures showing the number of sexual diseases diagnosed in Britain rose by 6 percent last year.
Substantial numbers of young people in particular still remain undiagnosed, untreated and unaware of the risk they pose both to their own health and that of their sexual partner.
Chlamydia is known as the silent disease because very often it does not have any obvious symptoms. Once diagnosed it can be easily treated with antibiotics.
Nearly one in 10 sexually active young women tested by a chlamydia screening programme in England last year were found to have the infection, which can cause pelvic inflammatory disease, ectopic pregnancy and infertility if left untreated.
People aged between 18 and 24 account for around half of all newly diagnosed sexually transmitted infections (STIs) in the UK but they form just one in eight of the total population.
This age group suffered 65 percent of all chlamydia cases, 55 percent of all genital warts and 50 percent of gonorrhoea infections diagnosed in genito-urinary clinics last year.
The total number of STIs diagnosed reached 397,990 in 2007, up from 375,843 the year before.
One reason for the rise could be an increase in the number being screened.
More than one million sexual health screens were conducted in 2007, ten percent more than in 2006.
If sustained, this could have a significant impact on the control of sexually transmitted infections.
One in 12 men was also found to be carrying the disease, the world's most common sexually transmitted infection.
A study by University College London last November showed that one in five young Britons has sex with a new partner when travelling abroad. Under these circumstances it is even more important to use protection and also to take a chlamydia test on your return home.
For more information about the home chlamydia test please click here.
