Chlamydia is sometimes called the 'silent disease' because you can have it without knowing it. As many as 8 in 10 women and 5 in 10 men who have chlamydia don't have any obvious signs of infection.

If you do get symptoms, they start one week to three weeks after you've been infected.^[4]

The most common symptoms in women are:^[4]

• Unusual discharge from the vagina

• Bleeding between periods

• Pain when passing urine

• Pain in the lower abdomen.

The most common symptoms in men are:^[4]

• Discharge from the penis

• Burning and itching around the genitals

• Pain when passing urine.

In men or women who have anal sex, chlamydia can cause inflammation in their back passage (rectum).^[5] This is called proctitis. Proctitis can cause pain, discomfort, bleeding, constipation, or an unusual discharge.

Symptoms of chlamydia may carry on, but sometimes they disappear after a few days.

If you're at risk of chlamydia and have one or more symptoms, you should see your doctor or visit your local sexual health clinic (also known as a genitourinary medicine, or GUM, clinic). You'll be offered a simple test that will show whether or not you have the infection.

The NHS is trying to make testing more widely available, especially for younger people. It's aimed at under 25s. In England, if you'd rather not see your GP or go to a GUM clinic, you can get testing from some pharmacies, drop-in centres, universities and family planning clinics. You can find out more at the NHS website (http://www.chlamydiascreening.nhs.uk) or by calling 0800 567123.

The test for chlamydia usually involves giving a urine sample. It can also be done with a swab. A swab is a twist of cotton at the end of a thin stick. Your nurse or doctor uses the swab to take a sample of fluid. The fluid can then be tested for the bacteria that cause chlamydia.

• If you're a woman, your doctor or nurse will usually take the swab sample from the neck of your womb (cervix).

• For men, the swab is put into the tip of the penis, a short way up the tube that carries urine (your urethra). Men usually prefer to give a urine sample, as taking a swab can be uncomfortable.^[6][7]

You can also get home test kits for chlamydia. These usually come with a bottle that you fill with urine and send off to a lab to be tested. You get the results by post. Some services can also send you the results by email or text.^[8]

Some test kits offer a result at home straight away, a bit like a home pregnancy test. But for the most reliable results, you'll need a test where you send a sample away to a lab.^[8]