Chlamydia is easy to treat and cure. But if it's not recognised and treated, chlamydia can spread. This can have serious effects on your health. If you're a woman you may find it hard to get pregnant.
If you don't have treatment
If you're a woman and you have chlamydia that isn't treated, it can spread to your ovaries, your womb, or the tubes that lead from your ovaries to your womb (fallopian tubes). When this happens it's called pelvic inflammatory disease (also called PID). Between 1 in 10 and 4 in 10 women who have chlamydia that hasn't been treated get pelvic inflammatory disease.
If you have pelvic inflammatory disease, you can have other problems such as:
Blocked tubes: If your tubes are blocked, you may not be able to get pregnant
Ectopic pregnancy: This is a dangerous condition. It happens when a fertilised egg can't move to your womb because of a blocked tube. And so your pregnancy starts growing in your fallopian tube.
About 1 in 10 women who've had just one attack of pelvic inflammatory disease get fertility problems because of their blocked tubes. And the risk of ectopic pregnancy goes up six or seven times.
If your tubes are damaged, they can sometimes be unblocked by having an operation.
If you're pregnant and have chlamydia that hasn't been treated, you can pass the infection on to your baby during birth. About one-third of babies born to mothers with untreated chlamydia have an infection of their eyes or their lungs at birth. But these infections can be cured with antibiotics.
If you're a man and you have chlamydia that isn't treated you're less likely to get serious health problems than a woman who has the infection. But sometimes chlamydia causes an inflammation either in the tubes leading to your testicles or in your testicles. This inflammation may make you less fertile (you may have problems getting a woman pregnant), but researchers don't know for certain.
Men can also get a form of arthritis known as Reiter's syndrome if they haven't had treatment for chlamydia.
If you have treatment
Having treatment with antibiotics (medicines that kill bacteria) cures chlamydia. But it doesn't stop you from getting infected again.
If you're a woman your risk of getting pelvic inflammatory disease goes up with each attack of chlamydia. And if you get pelvic inflammatory disease more than once, you're more likely to have fertility problems. (To read more see our information on Pelvic inflammatory disease.)
In the long term, the best way to protect yourself against chlamydia is to prevent the infection being passed between sex partners. Here's what doctors advise for men and women at risk of getting chlamydia.
Keep sex partners to a minimum.
Use condoms correctly and regularly during sex.
Get tested for chlamydia regularly. If you're under 24, get a test every year until you are 24.
Get a chlamydia test every time you have sex with someone new.
Some people choose to be tested when starting a new relationship. They may also ask their partner to be tested. (To read more about testing, see What are the symptoms of chlamydia?)