What Is It?

Chlamydia is a sexually transmitted disease (STD) spread by having unprotected sex with someone infected with bacteria called Chlamydia trachomatis. These bacteria are found in the urine and genital secretions of infected people. Chlamydia can affect several areas of the reproductive system, causing urethritis, vaginitis, cervicitis and pelvic inflammatory disease (PID). Chlamydia also can cause eye infections and pneumonia in newborns delivered by mothers who have chlamydia.

Chlamydia is one of the most common sexually transmitted diseases in the United States, with an estimated 4 million new infections occurring each year. Infections occur most often in unmarried people under age 25 who have had two or more sex partners during the previous year. In women, chlamydia that is not treated can lead to infertility, chronic pelvic pain and tubal pregnancy, in which the fertilized egg implants and grows in the fallopian tube, rather than the uterus. According to government health experts, about 50,000 women in the United States become infertile every year because of chlamydia.


About 75 percent of women and 50 percent of men with chlamydia have no symptoms. This is why many infected people remain untreated and can continue to spread the infection to others.

In women, chlamydia can cause:

  • A burning sensation when urinating
  • An abnormal vaginal discharge
  • Light vaginal bleeding (especially after intercourse)
  • Pain in the pelvis or lower abdomen

In men, chlamydia can cause:

  • An abnormal release of fluid that is not urine or semen (called penile discharge)
  • A burning sensation when urinating


Because chlamydia may not cause any symptoms, your doctor will gauge your risk of having the infection based on your sexual history. For example, your doctor will ask if you have had sex without using condoms. Your doctor can confirm whether you have chlamydia by using an extremely accurate urine test. Another way to test is by using a swab to collect fluid from the urethra or cervix. If you are at risk of chlamydia, you should be tested at least once a year, even if you have no symptoms.

Expected Duration

If untreated, chlamydia can last for many months, and during this time, bacteria can be spread to others through unprotected sex.


Because chlamydia is a disease that can be spread during sexual intercourse, you can prevent chlamydia by:

  • Not having sex
  • Having sex with only one, uninfected person
  • Always using male latex condoms during sexual activity

To prevent complications of untreated chlamydia, including infertility and tubal pregnancy, sexually active women at risk of chlamydia should have a routine pelvic examination with a chlamydia-screening test every year. To prevent chlamydia eye infections and pneumonia in newborns, all pregnant women should be screened for chlamydia.


Doctors treat chlamydia with oral antibiotics such as doxycycline (Vibramycin), azithromycin (Zithromax) and ofloxacin (Floxin). Everyone being treated for chlamydia should have all of his or her sex partners treated as well.

When To Call A Professional

All sexually active men and women should have routine physical exams every year, even if they have no symptoms of sexually transmitted diseases. In women, this physical exam should include a pelvic exam.

The U.S. Centers for Disease Control and Prevention recommends that all women who are pregnant or have a cervical infection see their doctors for chlamydia testing.

Men and women should have chlamydia screening at least once a year if they are:

  • Sexually active women under age 25
  • Sexually active women and men at a high risk for chlamydia (having a new sex partner, multiple sex partners, sex with men who do not use condoms)


Antibiotic treatment cures chlamydia and can prevent complications, although up to 20 percent of women who develop pelvic inflammatory disease from chlamydia may suffer long-term complications such as infertility or chronic pelvic pain.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.