Chlamydia is the most common sexually transmitted infection (STI) caused by bacteria. It often causes few or no symptoms, so regular screening is recommended for people at risk. If left untreated, chlamydia can cause serious complications, including pelvic inflammatory disease and infertility. People with STIs often experience shame or stigma, which can discourage timely testing and treatment.
Who is at risk for chlamydia?
Chlamydia is the most frequently reported bacterial STI in the United States, according to the Centers for Disease Control and Prevention (CDC). More than 1,640,000 cases were reported to the CDC in 2021, but many infections remain undiagnosed. After rising steeply over the past three decades, chlamydia cases appear to have leveled off in recent years, but this could be attributable to less STI testing during the COVID-19 pandemic.
Around two thirds of chlamydia cases occur among teenagers and young adults ages 15 to 24. It is most common among young women, but gay and bisexual men also have a high rate. Black men and women have about a sixfold higher chlamydia rate compared with white people, according to the CDC.
How is chlamydia transmitted?
Chlamydia trachomatis spreads primarily through vaginal, anal or oral sex. In addition to chlamydia, the same bacteria can also cause another STI, lymphogranuloma venereum. The bacteria are present in semen, pre-cum and vaginal fluid, and transmission can occur without ejaculation.
Pregnant people with chlamydia can transmit the bacteria to their babies during delivery, which can cause eye infections or pneumonia in the infant. Chlamydia is not transmitted through casual contact, such as hugging or kissing, or via shared objects such as toilet seats or eating utensils.
How can chlamydia be prevented?
Avoid having sex and get tested if you have symptoms that could indicate an STI. If diagnosed with chlamydia, inform your sex partners and hold off on having sex treatment is completed and symptoms resolve. But many people with chlamydia are asymptomatic or have such mild symptoms that they don’t know they have an STI. For this reason, the CDC recommends regular screening for men and women at risk, such as those with multiple sex partners.
Condoms and dental dams offer protection against chlamydia by preventing genital fluids from coming in contact with another person’s mucous membranes. Avoid sharing sex toys, cover them with a condom or clean them between users.
Recent research shows that taking the antibiotic doxycycline as post-exposure prophylaxis within 72 hours after sex—known as doxy PEP—reduces the risk of chlamydia, gonorrhea and syphilis for gay men and transgender women. However, this approach did not work for cisgender women in Africa.
Chlamydia does not confer lasting immunity, so it is possible to get it multiple times. There is currently no vaccine for chlamydia, but research is underway.
What are the symptoms of chlamydia?
A majority of people with chlamydia have few or no symptoms, but soome develop inflammation of the cervix (cervicitis), urethra (urethritis) or rectum (proctitis). Depending on the site of infection, symptoms may include pain or burning during urination, white or grayish discharge from the penis or vagina, rectal discharge and pain or a sore throat. These may not appear until several weeks after exposure. Chlamydia symptoms often resemble those of other STIs (especially gonorrhea) or urinary tract infections, so testing is the only way to know for sure. Less commonly, chlamydia can also affect the eyes, causing conjunctivitis.
If left untreated, chlamydia can lead to serious long-term complications. Cisgender women and transgender men can develop pelvic inflammatory disease, or infection of the reproductive organs. Symptoms may include fever, pain in the lower abdomen, pain or bleeding during intercourse and vaginal bleeding between menstrual periods. Over time, scar tissue can form around the uterus, fallopian tubes and ovaries, which may lead to chronic pelvic pain, infertility and ectopic pregnancy. Cisgender men and trans women can develop inflammation of the testicles or prostate.
Chlamydia and HIV
HIV-positive people with chlamydia are more likely to transmit the virus, and HIV-negative people with chlamydia are more likely to acquire HIV. People with chlamydia or other STIs should be tested for HIV if they don’t already know their status. People living with HIV, especially those who are not on antiretroviral treatment or have a low CD4 count, may have severe chlamydia symptoms.
How is chlamydia diagnosed?
Because chlamydia can resemble other conditions, testing is necessary to make a definitive diagnosis. Get tested if you have symptoms that could indicate chlamydia or if a sex partner has symptoms or tests positive.
Chlamydia is usually diagnosed with a urine test or using a swab to take a fluid sample from the vagina, penis, rectum or throat. Health care providers often test for gonorrhea at the same time. At-home tests for chlamydia and gonorrhea, which involve mailing a urine or vaginal fluid sample to a lab for analysis, can be purchased over the counter.
Regular screening—even if asymptomatic—is recommended for people at increased risk for STIs. The CDC recommends annual chlamydia testing for sexually active women under age 25 and older women at increased risk. Pregnant women should be tested at their first prenatal care visit. Men who have sex with men should be screened for chlamydia at least annually and every three to six months if they are at increased risk—for example, if they have multiple sex partners, are HIV positive or are taking pre-exposure prophylaxis (PrEP). Screening recommendations for transgender, nonbinary and gender diverse individuals should be based on their anatomy.
How is chlamydia treated?
Fortunately, chlamydia can be easily treated and cured with antibiotics. The usual treatment involves either a seven-day course of doxycycline pills or a single dose of oral azithromycin. These medications are safe and generally well tolerated, though they can cause gastrointestinal symptoms and increased sensitivity to sunlight. Even if symptoms improve, it’s important to take the full course of medication, as this will help prevent the development of drug resistance and ensure that chlamydia remains curable.
People should be reevaluated if symptoms continue for more than a few days after starting treatment. Avoid having sex until a week after starting treatment. The CDC recommends repeat testing three months after treatment. It is possible to get chlamydia again after successful treatment. Sex partners are often treated at the same time so that they don’t pass the infection back and forth. Although chlamydia can be cured, this does not reverse existing damage, so prompt testing and treatment are important.
Last Reviewed: November 17, 2023