Chlamydia is a sexually transmitted infection (STI) caused by the bacteria chlamydia trachomatis. It is passed from person to person by bodily fluids (semen and vaginal fluids) during sex. Chlamydia is very contagious, meaning it is easily passed from one person to another. It can be spread through:
If you have chlamydia while pregnant, you can pass it to your baby during childbirth.
Chlamydia is one of the most common STIs and is thought to affect around 1 in 10 sexually active young people in the UK. Because many people with chlamydia don’t know they have it, that figure may be much higher. Chlamydia is most common in people under 25 years of age.
There are 3 types of chlamydia bacteria that cause infection in humans.
Chlamydia trachomatis can cause infection in the genitals or different parts of the body including the:
Up to 80% of women and 50% of men with chlamydia experience no symptoms at all. For those that do have symptoms, they are often mild and may be ignored or overlooked.
Symptoms in women include:
Chlamydia symptoms in men include:
There are often no early signs of chlamydia, and it usually takes a few weeks for symptoms to develop after catching the infection. Some people don’t get symptoms until many months after they have been infected.
Because many people with chlamydia don’t have any symptoms, it's possible to have chlamydia for months or even years without knowing. You can still pass the infection on to other people even if you don’t have symptoms.
Chlamydia doesn’t usually cause any changes in how your genitals (penis and vagina) look, and it can’t be diagnosed by sight. To get an accurate diagnosis of chlamydia, you need to have a chlamydia test.
Often, chlamydia won’t make you feel any different at all as it can be symptomless.
But if you do get chlamydia and show symptoms, you may feel pain when you pee, stomach pain, rectal pain or discharge, pain in your genitals and bleeding (for women) after sex or between periods.
Chlamydia can cause pain or discomfort in your lower abdomen or rectum (in women) or testicles (in men). Women may also feel pain during sex and both sexes may experience a burning sensation when passing urine (peeing).
Chlamydia does not go away on its own and the infection will stay in the body until you get treatment.