Yes, chlamydia is a sexually transmitted disease (STD). It is one of the most common STDs in the United States, with over 1.5 million cases reported in 2024 alone. The infection is caused by a type of bacteria that spreads through vaginal, anal, or oral sex.
How Chlamydia Spreads
Chlamydia passes from person to person through vaginal fluid and semen. You can get it from vaginal intercourse, anal sex, or oral sex, and the bacteria can transfer even without penetration or ejaculation. Sharing sex toys with an infected partner is another route. A pregnant person with chlamydia can also pass it to their newborn during delivery.
The bacteria responsible for chlamydia can only survive inside human cells. Once it enters your body, it attaches to cells in the genital tract (or rectum or throat, depending on the type of contact), gets inside them, and reproduces. This is why the infection stays localized to the area of sexual contact and why you can have chlamydia in more than one site at the same time.
STD vs. STI: What’s the Difference?
You’ll see chlamydia called both an STD and an STI, and the terms are often used interchangeably. Technically, “sexually transmitted infection” refers to the presence of the bacteria in your body, while “sexually transmitted disease” implies the infection has caused symptoms or health problems. Since most people with chlamydia have no symptoms at all, many health organizations now prefer the term STI. In practice, both labels describe the same condition.
Why Most People Don’t Know They Have It
The majority of chlamydia infections produce no symptoms. This is the single most important thing to understand about the infection, because people unknowingly pass it to partners for weeks or months.
When symptoms do appear, they differ by sex. In men, the most common signs are burning during urination, discharge from the penis, and pain in the testicles. Women may notice a change in vaginal discharge, bleeding between periods or after sex, lower abdominal discomfort, burning when urinating, or itching. Anal infections in anyone can cause rectal pain, discharge, and bleeding. Oral infections almost never produce noticeable symptoms.
Who Should Get Tested
Because chlamydia so often flies under the radar, routine screening is critical. CDC guidelines recommend annual testing for all sexually active women under 25. Women 25 and older should be tested annually if they have a new partner, more than one partner, a partner with other partners, or inconsistent condom use outside a mutually monogamous relationship.
For men who have sex with women, there isn’t a blanket screening recommendation, though testing is encouraged in higher-risk settings like STI clinics or correctional facilities. Men who have sex with men should be tested at least once a year at all sites of sexual contact, and every three to six months if they’re on PrEP, living with HIV, or have multiple partners. Transgender and gender-diverse individuals should follow guidelines based on their anatomy and sexual practices.
Testing itself is straightforward. The standard method uses a urine sample for men or a vaginal swab for women. Self-collected vaginal swabs are just as accurate as those taken by a clinician, so a pelvic exam isn’t always necessary. If you’ve had oral or anal exposure, swabs from those sites can be tested too.
What Happens If It Goes Untreated
Left alone, chlamydia doesn’t resolve on its own and can cause serious damage. About 10 to 15 percent of women with untreated chlamydia develop pelvic inflammatory disease (PID), an infection of the uterus, fallopian tubes, and surrounding tissue. PID can cause chronic pelvic pain and scarring that leads to infertility or ectopic pregnancy. Chlamydia can also silently damage the fallopian tubes without ever producing symptoms, meaning reproductive harm can happen before a woman even knows she’s infected.
In men, untreated chlamydia can lead to infection in the tube that carries sperm, causing pain and, in rare cases, fertility problems. For anyone, having an active chlamydia infection also increases vulnerability to other STIs, including HIV.
Treatment and Recovery
Chlamydia is curable with a short course of antibiotics, typically lasting seven days. Treatment works well when taken as directed, and a follow-up “test of cure” isn’t routinely needed unless symptoms persist or there’s concern the medication wasn’t completed properly. You should avoid sex for seven days after starting treatment, or until you’ve finished the full course and symptoms have cleared. Your sexual partners need to be treated too, or reinfection is likely.
Retesting about three months after treatment is recommended for everyone, regardless of whether you think your partners were treated. Reinfection rates are high, and catching a repeat case early prevents further complications and further spread. If you can’t get retested at three months, do so at your next medical visit within a year.
How Common Chlamydia Really Is
Chlamydia is the most frequently reported bacterial STD in the United States. In 2024, provisional CDC data counted 1,515,985 cases: roughly 944,000 in women and 564,000 in men. Women are diagnosed at higher rates partly because screening guidelines target them more aggressively, not necessarily because they’re infected more often. The true number of infections is certainly higher than what’s reported, since so many cases never produce symptoms and never get tested.
Cases did decline 8 percent from 2023 to 2024, marking the second consecutive year of decline. Still, with nearly 446 cases per 100,000 people nationwide, chlamydia remains extremely common, particularly among young adults.