What is it?

Chlamydia is a common sexually transmitted infection caused by the bacterium Chlamydia trachomatis. It is one of the most frequently reported STIs worldwide, yet most people who have it experience no symptoms at all, making regular testing essential.

How it spreads

Chlamydia spreads through vaginal, anal, and oral sex with an infected person. It can infect the penis, vagina, cervix, anus, urethra, and throat. It can also be passed from a pregnant person to their baby during childbirth. Condoms significantly reduce the risk of transmission.

Symptoms

Most people with chlamydia have no symptoms. When symptoms occur, they may include:

  • Unusual discharge from the penis or vagina
  • Burning or pain when urinating
  • Pain or swelling in the testicles
  • Rectal pain or discharge
  • Pain during sex

Symptoms typically appear 7–21 days after exposure.

Testing

Chlamydia is diagnosed with a NAAT (nucleic acid amplification test) — a urine test or a swab of the affected area (cervix, urethra, rectum, or throat). Testing is recommended annually for all sexually active people under 25, and for older people with new or multiple partners. Home test kits are available.

Treatment

Chlamydia is curable with antibiotics:

  • 7-day course of doxycycline (recommended), or
  • Single dose of azithromycin (alternative)

Both you and your recent sexual partners should be tested and treated. Avoid sex for 7 days after treatment (or until all partners are treated). Untreated chlamydia can cause serious health problems including pelvic inflammatory disease and infertility.

Prevention

Prevention steps:

  • Use condoms or dental dams every time you have sex
  • Get tested regularly, especially if you have new or multiple partners
  • Talk openly with partners about STI status and testing

PrEP does not protect against chlamydia. Annual testing is the most effective prevention strategy alongside consistent condom use.