What Is Chlamydia? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Chlamydia is one of the most common sexually transmitted diseases (STDs) in the United States. It’s especially common in young adults, for reasons that have to do with both the biology of young bodies and the lifestyle choices made by many young people, such as having sex with many different partners.

While chlamydia can be easily and quickly treated, untreated chlamydia can — and often does — cause infertility in women. Symptoms of chlamydia can be mild or nonexistent, which means it’s important to get screened for it if you fit the recommended screening criteria.

“The signs of chlamydia are so subtle that women often don’t realize they have an infection,” says Jill Rabin, MD, the cochief of ambulatory care for women's health programs and prenatal care assistance services for Northwell Health in New Hyde Park, New York. And, she emphasizes, “Usually the disease has no symptoms” in women.

When symptoms occur, they tend to develop one to three weeks after exposure to chlamydia.

Chlamydia Symptoms in Women

In cases of chlamydia where symptoms occur, women may have one or more of the following symptoms:

• Pain or a burning sensation while urinating
• Abnormal vaginal discharge that may be watery or milky
• Painful discharge or bleeding from the anus
• Inflamed eyelids (from contact with genital secretions)

Advanced chlamydia may cause additional symptoms in women. The following symptoms indicate that chlamydia infection has spread to the fallopian tubes:

• Pain during sex
• Lower abdominal pain
• Bleeding between menstrual periods
• Nausea or fever

Chlamydia Symptoms in Men

Up to half of all men with chlamydia experience no symptoms. When men do have signs or symptoms, they may be minor and may include one or more of the following:

• Pain or burning while urinating
• An abnormal discharge from the penis, which may be pus (a thick yellowish-white fluid) or a watery or milky fluid
• Painful discharge or bleeding from the anus
• Inflamed eyelids (from contact with genital secretions)
• Painful or swollen testicles

Learn More About Symptoms of Chlamydia

Chlamydia is caused by bacteria called Chlamydia trachomatis. These bacteria attack the cells of your body’s mucous membranes — the soft, moist tissues of your body that aren’t covered by skin.

Here are areas of the body where mucous membranes are possible targets for chlamydia infection:

• Vagina, cervix, and fallopian tubes in women
• Urethra in women and men
• Anus and rectum
• Lining of the eyelid
• Throat (uncommon)

Although the bacteria that cause chlamydia can reach the uterus, “Chlamydia doesn’t attack the uterus itself, because a woman gets her period every month, and cells inside it are sloughed off,” says Dr. Rabin.

But the fallopian tubes — which connect the ovaries and uterus — do not clean themselves regularly, so they’re vulnerable to attack and lasting damage caused by the bacteria.

Chlamydia can be spread through any sexual contact, with or without ejaculation.

Chlamydia Risk Factors

While chlamydia can be spread through any sexual contact involving mucous membranes, certain activities — and certain people — are more likely to spread the infection.

Chlamydia is more likely to spread through genital-to-genital contact than from your mouth to someone’s penis, vagina, or anus, or from any of these areas to your mouth. That’s because the bacteria thrive in these other areas more easily than in your mouth or throat.

Young people are especially likely to get chlamydia, for a combination of behavioral, cultural, and biological reasons. Not using condoms consistently, moving quickly from one sexual relationship to another, and lack of access to STD screening services may all contribute to this increased risk.

Also, young people may be more vulnerable because “those young cells tend to attract the agents that cause chlamydia and other STDs, such as HPV [human papillomavirus], a bit more vigorously,” says Rabin.

Men who have sex with men are also considered to be at increased risk for chlamydia. In this group, the rate of positive chlamydia test results from a rectal swab ranges from 3.0 to 10.5 percent, and the rate from throat swabs ranges from 0.5 to 2.3 percent, according to the Centers for Disease Control and Prevention (CDC).

If you’re treated for chlamydia but your sexual partner isn’t, you can be reinfected by your partner, even if your partner is asymptomatic.

There are a few different types of diagnostic tests for chlamydia. The newest type, known as nucleic acid amplification tests (NAATs), can easily be performed on a swab of your vagina or a urine sample. Vaginal swabs are the preferred method to test for genital chlamydia in women, while urine samples are preferred for men.

Most labs aren’t approved by the U.S. Food and Drug Administration (FDA) to test rectal or throat swabs for chlamydia, but a doctor may still order these tests.

Who Should Get Tested for Chlamydia?

Pregnant women should be screened for chlamydia according to the above guidelines, with a second test during the third trimester of pregnancy. If a pregnant woman tests positive for chlamydia, she should be tested again three to four weeks after treatment to ensure that it was effective, plus once more within three months.

Men who have sex with men should also get screened for chlamydia yearly, with any potential areas of contact — urethra, rectum, or throat — included in these tests, regardless of whether condoms were used. Men in this group with multiple sex partners, or whose partner has multiple partners, should get tested every three to six months instead.

The CDC recommends screening all men for chlamydia at certain high-risk facilities, such as prisons and jails and STD clinics.

People with HIV should be tested for chlamydia at their first HIV evaluation, and at least once a year after that if they’re sexually active, depending on their sexual practices.

Notifying Sexual Partners

If you test positive for chlamydia, you should communicate this result to all sexual partners with whom you were intimate in the 60 days before the onset of symptoms or before your diagnosis — whichever is earlier. This recommendation applies to partners of all genders, with whom you’ve had anal, oral, or vaginal sex.

In some states, your healthcare provider is allowed to prescribe extra doses of antibiotics for you to give to your sexual partners — a practice known as expedited partner therapy (EPT). This practice has been shown to reduce the rate of chlamydia reinfection in the original person seeking treatment, as well as increase the reported rate of sexual partners getting treatment.

Prognosis of Chlamydia

“Chlamydia can be cured easily if it’s caught early,” Rabin says. If you receive prompt treatment with antibiotics, you can avoid the most damaging effects of chlamydia, such as severe pain or infertility in women.

If chlamydia isn’t promptly detected and treated, on the other hand, it can lead to a number of potentially serious complications.

If you become infected with chlamydia, any initial symptoms may occur one to three weeks after the time of infection. But in many people who test positive for chlamydia, there are no symptoms, and it’s impossible to pin down how long they’ve had the infection.

Chlamydia doesn’t go away on its own without treatment. If you don’t get treated, you may develop serious symptoms or complications.

A course of antibiotics is the treatment for chlamydia. Your doctor will decide which drug to prescribe, and at what dose, according to your individual medical needs and other aspects of your situation.

It’s important to abstain from having sex until seven days after the start of your antibiotic treatment, to prevent the transmission of chlamydia to a sexual partner. If you have a partner who is being treated for chlamydia, the same recommendation applies to them.

If you have symptoms that persist for more than a few days after you start your treatment, see your doctor again to be reevaluated.

Because the symptoms of chlamydia are similar to those of gonorrhea, you should be treated for both infections if you test positive for chlamydia. That’s because it’s often faster and cheaper to just treat both infections than to order another test for gonorrhea after a positive test result for chlamydia.

After completing your antibiotic treatment for chlamydia, you’ll need to get tested again after three to four months — or earlier, if recommended — to check for reinfection.

While antibiotics can cure chlamydia, they can’t reverse any permanent damage caused by the infection.

Medication Options

For adults and adolescents, the most common antibiotic regimens prescribed to treat chlamydia are as follows, taken by mouth:

• Azithromycin (1 gram single dose)
• Doxycycline (100 milligrams twice a day for seven days)

Alternative drugs that may be considered for special situations include the following:

• Amoxicillin
• Erythromycin
• Levofloxacin
• Ofloxacin

In some cases, including for some pregnant women, a lower dose of antibiotics may be taken up to four times a day, for as long as 14 days.

Learn More About Chlamydia Treatment and Prevention

Prevention of Chlamydia

There are a few steps you can take to reduce or eliminate your risk of getting chlamydia.

The only sure way to avoid chlamydia is to abstain from having vaginal, anal, or oral sex. You’re also highly unlikely to get chlamydia if you’re in a long-term monogamous relationship with a partner who has tested negative for the disease.

In other cases, using latex male condoms — correctly and consistently — can reduce your risk of getting chlamydia and other STDs. There isn’t enough data on preventing chlamydia transmission with other barrier methods (such as female condoms) for the CDC to recommend them.

If left undiagnosed and untreated, chlamydia can lead to serious complications in both women and men.

In women, untreated chlamydia can lead to the following complications:

• Pelvic inflammatory disease (PID)
• Cystitis (bladder inflammation)
• Cervicitis (cervix inflammation)
• Preterm delivery during pregnancy

PID, a serious infection of the reproductive organs, occurs with symptoms in about 10 to 15 percent of women with untreated chlamydia. But with or without symptoms, it can cause permanent damage to the fallopian tubes, uterus, and surrounding tissues, potentially resulting in chronic pelvic pain, infertility, or ectopic pregnancy (a sometimes fatal condition).

Cervicitis can sometimes cause a yellowish discharge from the cervix.

In men, untreated chlamydia can lead to the following complications:

• Prostatitis (inflammation of the prostate gland)
• Epididymitis (inflammation of the epididymis, a structure found behind each testicle)
• Scarring of the urethra
• Infertility

Prostatitis can come on gradually or suddenly, potentially causing severe pain.

In both women and men, chlamydia can increase the risk of HIV infection if you’re exposed to the virus.

Chlamydia is a very common infection, constituting the largest proportion of all STDs reported to the CDC since 1994.

The American Sexual Health Association (ASHA), for instance, estimates that as many as three million people have chlamydia each year in the United States.

Certain groups are much more likely to get chlamydia than the general population. For example, the rate of reported chlamydia in 2017 was about 39.9 cases per 1,000 people among women ages 20 to 24, and about 32.7 per 1,000 people among women ages 15 to 19.

Among men age 19 or younger who visited an STD clinic in 2017, nearly 40 percent of those who had sex with women tested positive for chlamydia. This number was nearly 30 percent for men ages 20 to 24 who had sex with women, and only slightly lower for men who had sex with men.

The rate of reported chlamydia varies widely throughout the United States at the county and state level. In 2017, West Virginia, Vermont, and New Hampshire had the lowest reported rates of chlamydia, while the highest rates were found in the District of Columbia, Alaska, Louisiana, and Mississippi. The region with the highest rate of chlamydia was the South, while the Northeast had the lowest rate.

The prevalence of chlamydia is drastically different across racial and ethnic groups in the United States. Overall, Black, American Indian and Alaska Native, and Native Hawaiian and other Pacific Islander women have the highest rates of chlamydia, according to the CDC.

In 2017, the reported rate of chlamydia in Black Americans was 5.6 times the rate of white Americans. Among Native Americans and Alaska Natives, this number was 3.7, and for Native Hawaiians and other Pacific Islanders, it was 3.4. Hispanic Americans were 1.9 times as likely to have chlamydia as white Americans, while Asian Americans were only 0.6 times as likely.

Among young women ages 14 to 24, the CDC estimates that the prevalence of chlamydia is about 10 percent for Mexican Americans, and about 8 percent for Black girls and women. This number is only about 2 percent for non-Hispanic white girls and women.

Gonorrhea This bacterial infection can cause symptoms and complications similar to those of chlamydia.

Genital herpes This viral infection is common, but most people with genital herpes don’t know they have it.

Human papillomavirus (HPV) The most common STD in the United States, this viral infection can cause genital warts and lead to cervical and other cancers. Many forms of HPV can be prevented by vaccines.

HIV/AIDS People who have other STDs are at increased risk for HIV infection, which is largely preventable through pre-exposure prophylaxis (PrEP) therapies.

You can protect your sexual health and fertility by educating yourself about STDs, as well as about healthy relationships and sexuality. If you’re sexually active, you should also get screened for STDs according to guidelines from the CDC.

The following resources can help provide information, support, and services related to sexual health.

CDC — Sexually Transmitted Diseases (STDs)

This online resource from the leading public health agency in the United States provides an overview of numerous STDs and related conditions, covering areas including prevention, testing, treatment, and statistics.

American Sexual Health Association

This nonprofit organization has online resources covering a wide range of topics, including STDs, sexual anatomy, sexual health in relationships, and talking to your kids about sex. It also has an online support group and discussion community with areas for specific STDs, STD prevention, and emotional and relationship issues.

National Coalition for Sexual Health

This coalition of more than 120 member organizations supports improving sexual health for all Americans by promoting high-quality sexual health information and health services. Its website has resources for the public and for healthcare providers, on topics like preventive health services, sexual health quick tips, and how to discuss sexual health at a doctor’s appointment.

Office on Women’s Health

This division of the U.S. Department of Health and Human Services provides information on numerous topics related to sexual and reproductive health, including STDs, relationships and safety, breastfeeding, and much more.

Planned Parenthood

This nonprofit organization operates clinics throughout the United States that provide STD testing and treatment, birth control, emergency contraception, abortion, and other sexual health services.

Learn More About Sexual Health Resources

Additional reporting by Quinn Phillips.