Chlamydia facts

What is chlamydia

Chlamydia is a sexually transmitted infection (STI) caused by a type of bacteria (Chlamydia trachomatis) that can be passed from one person to another during vaginal, anal, or oral sex.

How you get chlamydia

Chlamydia is usually spread during sex. It also can be passed from a pregnant person to the newborn during delivery and cause serious problems. Because most people do not have symptoms, it is easy to spread the infection without knowing it.

Symptoms of chlamydia

People with a vagina:

Up to 90% of those infected have no symptoms. Of those who do, symptoms may include:

• Vaginal discharge
• Unusual vaginal bleeding
• Burning or pain with urination
• Pain during sex

People with a penis:

Up to 70% of those infected have no symptoms. Of those who do, symptoms may include:

• Burning or pain with urination
• Pain or itching in the head of the penis
• Discharge from the penis
• Pain, tenderness, or swelling of the testicle(s)

Rectum:

Chlamydia can be transmitted to the rectum by an infected penis during anal sex. There are often no symptoms, but these infections may cause anal itching, pain, bleeding, or discharge.

Throat:

Chlamydia can be transmitted to the throat by an infected penis during oral sex. Most of the time there are no symptoms.

How serious is chlamydia

Chlamydia may cause a serious infection of the epididymis/testicles (balls) which can cause pain and lead to infertility (blockage of sperm).

In people with a vagina, chlamydia may lead to a serious infection called pelvic inflammatory disease (PID). PID can damage the fallopian tubes and make a “tubal pregnancy” (outside the uterus) more likely. PID can also lead to infertility, the inability to get pregnant.

Chlamydia can increase the risk of getting and passing HIV and other STDs. If you have been diagnosed with chlamydia make sure you also get tested for HIV.

Rectal chlamydia puts you at particularly high risk of getting HIV. If you have contracted rectal chlamydia and are HIV-negative talk to your health care provider about PrEP.

How to treat chlamydia

Treatment may be with an antibiotic taken twice daily for 7 days (doxycycline). If you are or might be pregnant, we would use one-time dose of a different antibiotic (azithromycin). It is important to finish all of the pills you are given, even if you feel better before taking them all.

Your sex partner(s) must be treated. Otherwise, they can give the infection back to you or infect others. You may ask for medicine to bring to your partner(s).

Don’t have sex for one full week after you start treatment. Don’t have sex with your partner(s) while you are each taking your medicine.

How to avoid getting or spreading chlamydia

• Condoms are effective in reducing the risk of infection.
• Ask your health care provider about doxy-PEP.
• Do not have sex if you or a sexual partner has symptoms of an STI, including discharge, burning with urination, rash, or genital sores.
• It is important to get tested again for chlamydia about 3 months after your treatment because if you have had chlamydia before, you may be more likely to get it again.

This information is provided by San Francisco City Clinic.

Visit our homepage at sf.gov/cityclinic.

Information last revised October 2025