What Is It?

Genital chlamydia is the most frequently reported bacterial sexually transmitted disease (STD) in the United States today. When diagnosed, chlamydia is easily treated and cured.

Genital chlamydia (pronounced kla-mid-ee-uh), a bacterial sexually transmitted disease (STD) caused by the bacterium Chlamydia trachomatis, is the most frequently reported communicable disease in the United States today.

According to the U.S. Centers for Disease Control and Prevention (CDC), chlamydia occurs most often among teenagers and young adults. In fact, the highest rates of chlamydia occur in girls aged 15 to 24. Overall, an estimated one in 20 sexually active young females aged 14 to 24 is infected with chlamydia, according to the CDC.

Initially, in females, the bacteria invade cells lining the endocervix (the opening to the uterus). If chlamydia remains untreated, it may spread into the upper reproductive tract and can eventually lead to infertility, ectopic pregnancy and chronic pelvic pain.

Chlamydial infections in women are usually asymptomatic. It has been estimated that chlamydia causes no symptoms in 90 percent of males and 70 percent to 95 percent of females. It is sometimes called a "silent" disease. Because chlamydia is usually silent but can lead to serious complications, such as infertility, routine annual screening of all sexually active females younger than 25 years of age is recommended.

When diagnosed, chlamydia is easily treated and cured. Left untreated, it can lead to significant medical problems for females, one of the most serious being pelvic inflammatory disease (PID). PID is a generic term indicating various inflammatory disorders of the upper genital tract, including endometritis (inflammation of the endometrium or lining of the uterus) and tubo-ovarian abscess (infection involving the fallopian tube and ovary). Acute PID can be difficult to diagnose. Its signs and symptoms vary widely, and many females have only subtle symptoms.

In addition to PID, chlamydia can lead to proctitis (inflamed rectum) and conjunctivitis (inflammation of the eye lining). It also increases risk for HIV and other STDs, as well as cervical cancer.

Chlamydia and PID

The following factors may increase your risk for developing PID:

  • previous episodes of PID or STDs
  • multiple sex partners or a partner with multiple sex partners
  • being under age 25
  • douching

It's a common misconception that the use of an intrauterine device (IUD) increases the risk of developing PID. The risk of developing PID is minimally increased during the first 20 days after insertion of the device, but after that time the risk returns to baseline. This risk can be reduced by testing for STDs before IUD insertion and treating appropriately. IUDs are an extremely safe and effective means of preventing pregnancy, with less than 1 percent unintended pregnancies per year.

Chlamydia infection is one of the most common causes of PID. It has been estimated that 10 percent to 15 percent of females with untreated chlamydia will develop symptomatic PID. Some females with PID will become infertile. Other potential complications include chronic pelvic pain and life-threatening ectopic pregnancy, which is a leading cause of pregnancy-related deaths for American females in the first trimester.

Annual chlamydia screening for sexually active females under 25 years old is cost effective because it can prevent serious reproductive complications.

Chlamydia and HIV

Research has shown that females infected with chlamydia are up to five times more likely to acquire HIV if exposed to the virus. The reason for the increased risk may be that chlamydia causes a spike in the number of white blood cells at the site of infection. Some of these immune system cells, while needed to fight the infection, also happen to be the main target for HIV.

Chlamydia and Cervical Cancer

Some studies have shown an increased risk of cervical cancer in females who have had chlamydia. A 2016 review of 22 studies published in the journal Medicine concluded that infection with Chlamydia trachomatis may increase the risk of cervical cancer in infected females. Although infections with cancer-causing strains of human papillomavirus (HPV) remain the prime cause of cervical cancer, infection with certain subtypes of Chlamydia trachomatis may contribute to that risk, according to the review.

All medical professional associations, such as the American College of Obstetricians and Gynecologists, the American Academy of Pediatrics and the American Association of Family Physicians, recommend routine chlamydia screening annually for all females under 25. As a result, more public and private health care professionals have been screening young females.

However, most young females are still not tested regularly for chlamydia, leading health officials to estimate that the actual number of infections is much higher than reported.

Reported female cases greatly exceed those for males. The reasons for this are unclear, yet it may be that fewer men are tested routinely for chlamydia, often presenting for testing only when they have symptoms.

Fortunately, increased awareness of the seriousness of chlamydia has put pressure on health care professionals to offer regular screening to younger females. In the year 2000, chlamydia was added to the list of performance measures for the Healthcare Effectiveness Data and Information Set, known by its acronym HEDIS. This tool rates how well managed care organizations perform on a variety of clinical measures, including prevention efforts for breast cancer, controlling blood cholesterol levels and childhood immunizations. While this step does not make chlamydia screening mandatory, managed care organizations are evaluated on how well they meet the established guideline of offering yearly chlamydia testing to sexually active females between ages 16 and 24 years.

In addition, the Patient Protection and Affordable Care Act (ACA) requires insurance companies to cover the cost of chlamydia screening, as well as some other STD testing and prevention counseling.

Chlamydia in Pregnancy

A small percentage of pregnant females are infected with chlamydia. In pregnant females, untreated chlamydia has been associated with pre-term delivery. Transmission to the newborn results from exposure to the mother's infected cervix during birth. All females should be screened for chlamydia as part of routine prenatal care.

Infants with chlamydia may be born prematurely. They also may experience eye inflammation (conjunctivitis) and breathing problems. Chlamydia infection also can involve the oropharynx, genital tract and rectum. Infection sometimes can cause pneumonia during an infant's first months. Recommended treatment for neonatal chlamydia is erythromycin base divided in four daily doses for 14 days. The alternative treatment is azithromycin, one dose daily for three days.


Part of what makes chlamydia so difficult to diagnose is that it is largely asymptomatic; in other words, someone can be infected for months or longer and never know they have the infection.

When symptoms do occur, they often are mild—a burning sensation when urinating and/or a discharge from the vagina or penis are typical symptoms. Females may also experience pain in the pelvic area or discomfort or bleeding during sex. Health care professionals may not address these symptoms, possibly leading to the chlamydia infection remaining untreated. If left untreated in females, it may result in PID and its complications.

PID can occur within days or several months after being infected with chlamydia. At this point, symptoms still may go unnoticed in some females, yet they do have an active PID infection. Other females, however, may experience bleeding between menstrual periods, lower back pain, pain during sexual penetration, increased vaginal discharge and severe pelvic pain.

Testing is the only way to know whether you have chlamydia. The CDC recommends annual screening for all sexually active females under 25 years of age and for older females with risk factors (such as, those who have a new sex partner and those with multiple sex partners). All females with signs of infection of the cervix and all pregnant females should be tested.

The most sensitive chlamydia tests, called nucleic acid amplification tests, can be performed on a urine specimen or a self-collected vaginal swab. For a female with no symptoms, an invasive genital exam is usually not required. However, a chlamydia test can also be performed on a swab of the cervix collected as part of a pelvic exam or a urethral swab collected on males. It may take several days before you can get a test result.


If you test positive for chlamydia, your infection can be cured with antibiotics. Depending on several factors, your health care professional may prescribe a single dose of 2 or 4 pills of azithromycin, or may prescribe doxycycline, which requires one pill twice a day for seven days.

If you are pregnant and infected with chlamydia, you still can be treated without harming the fetus. The recommended regimen for pregnant females is azithromycin pills taken in a single dose. Doxycycline is not recommended during pregnancy. As with any antibiotic treatment, it is important that you take all prescribed pills.

Too often, females become reinfected with chlamydia because their partner has not been treated. Studies have shown that females who are reinfected with chlamydia have a much greater risk of developing PID. Therefore, it is important that you abstain from sexual contact until a week after your partner has been tested and completed treatment, meaning seven days after a single-dose azithromycin regimen or after completion of a seven-day doxycycline regimen.

In addition, you should return to your doctor for a repeat test three to six months after you are treated to be sure that you have not been infected again.

In general, treatment is recommended for any partner or partners you had sexual contact with up to 60 days prior to having symptoms or a diagnosis of chlamydia, or the last partner you had sexual contact with before you were diagnosed. Some clinics and doctors' offices offer what is called expedited partner therapy (EPT). Patients are given a prescription or the medication that treats chlamydia to give to their partner(s) without the clinician assessing the partner. There are legal and ethical debates about this approach, and it does have some limitations (including loss of screening and counseling opportunities and the rare potential for adverse reactions to antibiotics), but in some cases it may be the most effective way to stop the spread of chlamydia, because many infected partners have no symptoms and are reluctant to seek treatment.

EPT is legal in many U.S. states and cities. Learn more about the Legal Status of Expedited Partner Therapy.

In some cases, people infected with chlamydia are also infected with gonorrhea. Therefore, testing for gonorrhea is often done at the same time as testing for chlamydia. If a person tests positive for both infections, additional treatment is necessary.

PID Treatment

PID treatment begins with an antibiotic regimen that provides broad coverage against several bacteria. Treatment should begin as soon as a diagnosis is made, because immediate therapy has been shown to reduce the risk of long-term consequences of PID.

Antibiotics may be given by mouth or injection. There are several treatment options recommended by the CDC. Regardless of which type of therapy is chosen, hospitalization is no longer recommended, however, it may be considered in certain circumstances including:

  • Surgery is needed.
  • An oral outpatient regimen cannot be tolerated.
  • A patient is pregnant.
  • A patient does not respond clinically to oral antimicrobial therapy.
  • A patient has severe illness, including high fever and vomiting.
  • A patient has tubo-ovarian abscess or a weakened immune system.

While medication can stop PID, some females may need surgery to remove scar tissue and blockages caused by long-term infection.


Protecting yourself from chlamydia requires the same care and attention needed to prevent other sexually transmitted diseases (STDs). If you have already been infected, you should be vigilant in preventing reinfection, which can increase your risk of infertility.

Abstinence is one sure way not to become infected, as the spread of chlamydia is almost always limited to sexual contact. If you have sex, make sure you use a latex condom from the beginning to the end of sexual contact every time you have sex. Latex condoms offer the best available means of reducing your risk of contracting an STD when they are used consistently and correctly. Polyurethane condoms are available for latex-sensitive or allergic individuals which provide similar protection against STDs, HIV and pregnancy compared to latex condoms.

Also know that your risk for chlamydia infection increases with the more sexual partners you have. If you are sexually active and under 25 years of age, or if you are older but have any risk factors for chlamydia, you should ask your provider to test you at least once a year. Risk factors include being young and sexually active, having multiple sex partners and having previous infection with other STDs.

Women who have sex with women—either exclusively or in addition to male partners—are also at risk for chlamydia. Women who have sex exclusively with women may be at a decreased risk, but they should still take precautions.

Sexually active individuals should consider the following precautions to protect themselves from contracting these diseases:

  • Reduce your number of sex partners.
  • If you have sex with a male partner, always use a condom from start to finish during any type of sex (vaginal, anal and oral). Use latex condoms rather than natural membrane condoms. If used consistently and correctly, latex condoms offer greater protection against STD agents, including HIV. Polyurethane condoms are available for latex-sensitive or allergic individuals.
  • Use only water-based lubricants. Oil-based lubricants such as petroleum jelly and vegetable shortening can destroy condoms. If you decide to use a spermicide along with a condom, it is preferable to use spermicide in the vagina according to manufacturer's instructions. The U.S. Food and Drug Administration (FDA) requires a warning on the labels of over-the-counter vaginal contraceptives that contain the spermicide nonoxynol-9. The warning states that vaginal contraceptives containing nonoxynol-9 do not protect against infection from HIV/AIDs or other STDs. The FDA's warning also advises consumers that the use of vaginal contraceptives containing nonoxynol-9 can increase vaginal irritation, which may increase the possibility of transmitting HIV and other STDs from infected partners.
  • Get tested for chlamydia once a year if you are 24 years or younger or have other risk factors.
  • Ask your sexual partners to get tested if they are 24 years of age or younger or have other risk factors.
  • Get tested more frequently if you or your sexual partners develop symptoms such as discharge from the vagina or penis, burning with urination or bleeding during sex.


Scientists are looking for better ways to diagnose, treat and prevent chlamydia infections. Researchers supported by the National Institute of Health recently completed sequencing the genome for Chlamydia trachomatis. The sequence represents an encyclopedia of information about the organism. This accomplishment will give scientists important information as they try to develop a safe and effective vaccine. Developing topical microbicides (preparations that can be inserted into the vagina to prevent infection) that are effective and easy for females to use is also a major research focus.

Facts to Know

1. Nearly two-thirds of new chlamydia infections take place in individuals aged 15 to 24 years old.

2. Studies have shown that routine chlamydia screening and treatment can significantly reduce the incidence of lower genital tract chlamydia, as well as PID, ectopic pregnancy, chronic pelvic pain and infertility.

3. An estimated 70 percent to 95 percent of infected females and 90 percent of infected males have no symptoms of chlamydia, and the majority of cases go undiagnosed.

4. According to the CDC, in 2015, there were 1,526,658 reported cases of chlamydia. These numbers are on the rise. However, rather than evidence of an uncontrolled epidemic, part of this trend reflects increased screening of asymptomatic females and improved reporting.

5. Research has shown that females infected with chlamydia are significantly more at risk of acquiring HIV than females not infected.

6. It has been estimated that 10 percent to 15 percent of females not treated for chlamydia will develop PID. Left untreated, PID may lead to infertility, chronic pelvic pain or life-threatening ectopic pregnancy.

7. The Southern region of the United States has the highest reported rates of chlamydia. Rates of chlamydia have consistently been the lowest in the Northeast.

8. According to CDC, the rate of chlamydia among African-American females is 5.9 times higher than the rate among Caucasians.

Questions to Ask

Review the following Questions to Ask about chlamydia so you're prepared to discuss this important health issue with your health care professional.

  1. If chlamydia is often without symptoms, how do I know if I have been infected?
  2. If I don't treat chlamydia, what will happen?
  3. What treatments are available?
  4. What should I tell my partner?
  5. How long should I abstain from sex after treatment begins?
  6. What are the symptoms of pelvic inflammatory disease?
  7. Is it possible I am infected with gonorrhea as well?
  8. Is chlamydia transmitted by sexual intercourse only?
  9. Do I need to be retested after treatment to be sure I am cured?

Key Q&A

What is chlamydia?

Chlamydia infection is caused by a bacterium called Chlamydia trachomatis. The bacterium can be transmitted during sexual intercourse or by oral-genital contact with an infected person.

If so many people with chlamydia don't have symptoms, why is it necessary to get treated?

Even though infection often is asymptomatic, it can still cause serious consequences for females, and for pregnant females and their infants. Also, the only way to stop the epidemic is by treating everyone infected, whether they have symptoms or not.

How will chlamydia infection affect my chances of getting pregnant?

It depends on several factors, such as how long you have been infected and whether the infection has migrated into your upper genital tract. Pelvic inflammatory disease, which is often caused by chlamydia infection, can lead to infertility.

Does having chlamydia put me at greater risk for other sexually transmitted diseases (STDs)?

Yes. Chlamydia infection increases your risk of HIV by producing more of the type of white blood cells to which HIV attaches itself. Individuals are also frequently infected with more than one STD at a time. These STDs are often transmitted at the same time, so if you have acquired chlamydia, you may also be at risk for having other STDs.

What are the side effects of chlamydia treatment?

Chlamydia can be cured with antibiotics without causing significant side effects. The most common side effects are upset stomach, nausea, vomiting and diarrhea.

How is pelvic inflammatory disease treated?

In most cases, the first line of treatment is oral antibiotics. More serious cases or special circumstances may require intravenous drugs and hospitalization.

Why are more females diagnosed with chlamydia than males?

One reason is that unless they have symptoms, most males are never tested for chlamydia. Females, on the other hand, although they are more likely not to have symptoms of the disease, do have annual exams and therefore more opportunities to be screened for infection.

Can a pregnant females pass chlamydia to her infant?

Yes. The infection can be transmitted during birth and can cause eye and lung infection in a newborn. Fortunately, a pregnant female can take medication that will cure chlamydia without harming her or her child.

Lifestyle Tips

1. Prevent pelvic inflammatory disease

Pelvic inflammatory disease, or PID, occurs when untreated infection, often a sexually transmitted infection such as chlamydia, spreads to the uterus, fallopian tubes or ovaries. Although many females have mild or nonexistent symptoms, some notice pain in the lower abdomen, vaginal discharge or bleeding, painful intercourse, nausea and vomiting and fever. Untreated PID can lead to tubal infertility, chronic abdominal pain or ectopic pregnancy. To prevent PID, make sure you are screened annually for chlamydia if you are 24 years or younger or have other risk factors. Also, your partners should be screened for STDs, particularly chlamydia and gonorrhea. You should also limit the number of sex partners you have, and use condoms every time you have sex.

2. Practice the best protection
After abstinence, the best protection against any type of STD is a latex condom. Polyurethane condoms are available for latex-sensitive or allergic individuals. However, condoms don't provide 100 percent protection against STDs—only abstinence does. If you use a condom, make sure you use it properly. Human error causes more condom failures than manufacturing errors. Use a new condom with each sexual act (including oral sex). Carefully handle it so you don't damage it with your fingernails, teeth or other sharp objects. Put the condom on after the penis is erect and before any genital contact. Pinch the tip of the condom to leave room for semen collection. Use only water-based lubricants with latex condoms. Ensure adequate lubrication during intercourse. Hold the condom firmly against the base of the penis during withdrawal, and withdraw while the penis is still erect to prevent slippage.

3. Get tested for STDs
No single test screens for all STDs. Some require a vaginal exam, others a blood or urine test. A negative test does not always ensure you do not have an infection. Still, it's important to ask your health care provider to regularly test you for STDs if you're sexually active in a non-monogamous relationship (or have the slightest concern about your partner's fidelity). You can get tested at your health department, community clinic, private doctor or Planned Parenthood. Or call the CDC at 1-800-CDC-INFO (1-800-232-4636) or visit the CDC website to find free or low-cost clinics in your area.

5. Know whether you have an STD
While some STDs are accompanied by symptoms such as sores/ulcers or discharge, most, unfortunately, have no symptoms. You can't always tell if you or a partner has an STD just by looking. Don't rely on a partner's disclosing and assume that will prevent you from acquiring an STD; many infected persons do not know they have a problem. They may think symptoms are caused by something else, such as yeast infections, friction from sexual relations or allergies. Educate yourself about your own body and, in turn, learn about your own individual risk for contracting an STD. One way to do this is to schedule an examination with a health care provider who can sit down with you and help you learn the principles for staying safe and sexually healthy. Don't allow fear, embarrassment or ignorance to jeopardize your future.

6. Talk to your children about STDs
Sexually transmitted diseases are particularly common among adolescents. And it's an issue kids are concerned about. As a parent, you can play a large role in an adolescent's behavior, both in terms of the behavior you model yourself and in terms of the communication between you and your teen. Talk to your kids. Study after study proves that when parents talk to their kids about sexual issues, their kids listen. Don't worry that talking about sex is the same as condoning it; numerous studies dispute that theory. In fact, studies show that when parents talk about sex, children are more likely to talk about it themselves, to delay their first sexual experiences and to protect themselves against pregnancy and disease when they do have sex. Also, make sure your daughters or sons see a medical professional who is sensitive to adolescent health issues at least once a year, if for nothing else than to talk about STDs and pregnancy.

Organizations and Support

For information and support on coping with Chlamydia, please see the recommended organizations, books and Spanish-language resources listed below.

American College of Obstetricians and Gynecologists (ACOG)
Website: https://www.acog.org
Address: 409 12th Street, SW
P.O. Box 96920
Washington, DC 20090
Phone: 202-638-5577
Email: resources@acog.org

American Social Health Association (ASHA)
Website: https://www.ashasexualhealth.org/
Address: P.O. Box 13827
Research Triangle Park, NC 27709
Hotline: 1-800-227-8922
Phone: 919-361-8400
Email: info@ashastd.org

ASHA's STI Resource Center Hotline
Website: https://www.askexpertsnow.com/
Address: American Social Health Association
P.O. Box 13827
Research Triangle Park, NC 27709
Hotline: 1-800-227-8922
Phone: 919-361-8400

CDC National Prevention Information Network
Website: https://www.cdcnpin.org
Address: P.O. Box 6003
Rockville, MD 20849
Hotline: 1-800-458-5231
Phone: 404-679-3860
Email: info@cdcnpin.org

Guttmacher Institute
Website: https://www.guttmacher.org
Address: 1301 Connecticut Avenue NW, Suite 700
Washington, DC 20036
Hotline: 1-877-823-0262
Phone: 202-296-4012
Email: info@guttmacher.org

National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention
Website: https://www.cdc.gov/nchhstp
Address: Centers for Disease Control and Prevention
1600 Clifton Road
Atlanta, GA 30333
Hotline: 1-800-CDC-INFO (1-800-232-4636)
Email: cdcinfo@cdc.gov

National Family Planning and Reproductive Health Association (NFPRHA)
Website: https://www.nfprha.org
Address: 1627 K Street, NW, 12th Floor
Washington, DC 20006
Phone: 202-293-3114
Email: info@nfprha.org

Planned Parenthood Federation of America
Website: https://www.plannedparenthood.org
Address: 434 West 33rd Street
New York, NY 10001
Hotline: 1-800-230-PLAN (1-800-230-7526)
Phone: 212-541-7800

Sexuality Information and Education Council of the United States (SIECUS)
Website: https://www.siecus.org
Address: 90 John Street, Suite 704
New York, NY 10038
Phone: 212-819-9770


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by Michael V. Reitano, Charles Ebel

Sex: What You Don't Know Can Kill You
by Joe S. McIlhaney, Marion McIlhaney

Spanish-language resources

Medline Plus: Chlamydia
Website: https://www.nlm.nih.gov/medlineplus/spanish/ency/article/001345.htm
Address: Customer Service
US National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894
Email: custserv@nlm.nih.gov

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