Chlamydia is a curable bacterial infection caused by Chlamydia trachomatis, spread through vaginal, anal, or oral sex. It's the most commonly reported STI in the US, and most people who have it feel nothing at all. A short course of antibiotics clears it. Most cases turn up through screening, not symptoms.
urine or swab
after exposure
100 mg 2×/day, 7 days
catches reinfection
| Item | Value |
|---|---|
| Test method | NAAT — urine or swab |
| When to test | ~2 wks — after exposure |
| Treatment | doxycycline — 100 mg 2×/day, 7 days |
| Retest | 3 mo — catches reinfection |
What chlamydia actually is
Chlamydia is an infection of the genital, rectal, or throat tissues caused by the bacterium Chlamydia trachomatis. Most genital infections in the US come from serovars D–K, which infect the mucous lining of the cervix, urethra, rectum, and throat CDC, About Chlamydia. The bacterium lives inside cells, so infections can simmer quietly without triggering obvious inflammation. It's the most-reported bacterial STI in the country, with roughly 1.65 million reported cases in 2023, a rate that has stayed roughly flat across 2020–2023 CDC AtlasPlus, 2023. The burden isn't even. Washington DC, Louisiana, and Mississippi report rates more than double the national average.
And it's curable. The right antibiotics reliably clear the infection. But "cured" only applies to the infection you treated; nothing about treatment protects you from catching it again from an untreated partner.
Symptoms — and the silent reality
Chlamydia usually causes no symptoms. About three quarters of infected women and half of infected men have nothing to notice CDC Fact Sheet. You can't wait to "feel sick" — by the time symptoms show, the infection has often been present for a while and may have spread. When symptoms do appear, they usually show up within one to three weeks after exposure.
In women
Women may notice an abnormal vaginal discharge or burning during urination. If the infection climbs from the cervix into the upper reproductive tract, it can cause lower abdominal or low-back pain, fever, pain during intercourse, and bleeding between periods. These signs warrant prompt care because they suggest the infection is no longer confined to the cervix.
In men
Men may see a penile discharge that's clear or cloudy, sometimes only a single drop in the morning, along with burning on urination and itching or burning at the tip of the penis. Less often, the infection causes testicular pain or swelling. These signs are subtle and easy to dismiss, so many men never connect them to an STI. There's a fuller breakdown of chlamydia symptoms in men.
Rectal and throat infections
Rectal chlamydia can cause rectal pain, discharge, or bleeding, but it's frequently silent. Throat (pharyngeal) infections are typically asymptomatic entirely. This matters for testing: a genital test won't detect an infection sitting in the rectum or throat, so the sites you test need to match the sex you've had.
How chlamydia spreads
Chlamydia passes through vaginal, anal, or oral sex with an infected person. It doesn't require ejaculation or visible symptoms; contact between mucous membranes is enough. A pregnant woman can also pass it to her baby during childbirth, which is why prenatal screening matters. It does not spread through toilet seats, towels, or casual contact.
How it's tested
The recommended and most accurate test is a NAAT (nucleic acid amplification test), which detects the bacterium's genetic material and works for genital and extragenital sites CDC STI Tx Guidelines, 2021. Specimens can be a first-catch urine sample, or swabs of the vagina, cervix, male urethra, rectum, or throat. The vaginal and rectal swabs can be self-collected, with no speculum or uncomfortable urethral swab needed for the standard approach.
In practice, testing is quick: you pee into a cup (hold your urine for about an hour beforehand for the best sample) or do a self-swab, and results are often texted back within a day or three. There's no blood draw for a chlamydia NAAT. Testing the morning after a hookup is a common and costly mistake, because a NAAT is most reliable about two weeks out, and an early negative can falsely reassure you. See when to test after exposure for the timing, and when you're ready you can get tested or compare testing providers.
Who should be screened
The USPSTF gives a Grade B recommendation to screen all sexually active women 24 and younger, plus women 25 and older at increased risk, including during pregnancy USPSTF, 2021. For men, the evidence is judged insufficient (an "I statement") — not because men can't get it, but because the serious complications like infertility fall on women, so the screening case is strongest there. The CDC additionally recommends at least annual screening for sexually active men who have sex with men at every site of exposure — urethra, rectum, and throat — and every three to six months for those at higher risk, plus an HIV test for anyone diagnosed with chlamydia.
Treatment: what cures it
The preferred treatment is doxycycline, taken as a pill twice daily for seven days CDC Chlamydial Infections. Take it with food and avoid strong sun, since it can make you burn more easily. Alternatives include a single dose of azithromycin or a seven-day course of levofloxacin once daily. In pregnancy, a single dose of azithromycin is preferred (with amoxicillin three times daily for seven days as an alternative).
Doxycycline became first-line over the older single-dose azithromycin for a concrete reason: azithromycin showed higher microbiologic failure in men and was markedly weaker against rectal infection. In one randomized trial, doxycycline cured 100% of rectal infections versus 74% for azithromycin Rectal CT RCT. For full regimens and details, this is a hub article.
Partners, abstinence, and not bouncing it back
Treating yourself isn't enough if your partner is still infected; that's the "ping-pong" cycle. Refer, test, or presumptively treat partners from the prior 60 days. Abstain from sex for seven days after single-dose therapy, or until you've finished the seven-day course. Expedited partner therapy (EPT), where you're given medication to deliver to a partner, measurably reduces repeat infection. A landmark trial found persistent or repeat infection dropped, with the largest benefit for gonorrhea (3% versus 11%) Golden et al., NEJM. EPT is permissible in most but not all US states, so verify your local status.
When to retest
Put a retest about three months after treatment on your calendar to catch reinfection. It's not a test-of-cure, and most people don't need a test-of-cure unless they're pregnant, didn't finish the medication, still have symptoms, or reinfection is suspected. Pregnant people are the exception: a test-of-cure about four weeks after finishing, plus a retest at three months. More on why this matters in chlamydia reinfection.
What happens if it's left untreated
Untreated chlamydia is dangerous because it's silent, with damage accumulating without warning.
- In women: pelvic inflammatory disease (PID, infection that spreads to the uterus and tubes), fallopian-tube scarring, ectopic pregnancy (a pregnancy implanting outside the uterus, which can be life-threatening), infertility, and chronic pelvic pain.
- In men: epididymitis (inflammation of the coiled tube behind the testicle that causes pain and fever, and rarely affects fertility).
- In anyone: reactive arthritis (joint inflammation, formerly called Reiter syndrome, that can follow the infection).
- In newborns: chlamydia is a leading cause of early infant pneumonia and conjunctivitis (eye infection) when passed during childbirth.
- HIV risk: having chlamydia may increase your risk of acquiring or transmitting HIV.
Prevention that actually works
Condoms used correctly every time lower your risk, and a long-term mutually monogamous relationship with a tested partner is protective. But because most infections cause no symptoms, routine screening and treating partners are what move the needle. DoxyPEP, a single 200 mg dose of doxycycline within 72 hours of sex, reduces chlamydia by more than 70% and is offered to men who have sex with men and transgender women who've had a bacterial STI in the past year CDC DoxyPEP, 2024. Read the full picture on how to prevent chlamydia.
What testing and treatment cost
Testing is free or low-cost at Planned Parenthood, health departments, and Title X clinics; at-home kits typically run about $50–150, and it's often $0 with insurance. Testing positive is routine and curable; clinics handle it every day, and in many states you can notify partners anonymously. It's a treatable infection, not a verdict on your character.
When to see a clinician
See a clinician if you have any genital discharge, burning on urination, pelvic or testicular pain, or bleeding between periods. Don't wait for symptoms if you've had a new or untreated partner, since most infections are silent. Get screened if you fall into a recommended group, and seek prompt care for lower abdominal pain with fever, which can signal PID. If you're pregnant, screening is part of standard prenatal care.