Chlamydia is the most commonly reported bacterial sexually transmitted infection in the United States, and while it’s easily curable with antibiotics, leaving it untreated can cause serious, sometimes permanent damage to your reproductive system. The real danger lies in how quietly it operates: 75% of women and 50% of men with chlamydia have no symptoms at all, meaning the infection can silently progress for weeks or months before anyone knows it’s there.
Why Silent Infections Are the Biggest Risk
Chlamydia earns its reputation as a “silent” infection because most people who have it feel completely fine. Without symptoms like unusual discharge, burning during urination, or pelvic pain to prompt a test, the bacteria can linger and spread to surrounding tissue. This is where the danger starts. The longer the infection goes undetected, the more time it has to trigger inflammation in the reproductive tract, and that inflammation is what leads to lasting harm.
Because so many cases are symptomless, routine screening is the primary way chlamydia gets caught early. The U.S. Preventive Services Task Force recommends annual screening for all sexually active women aged 24 and younger, and for older women with risk factors like a new sexual partner, multiple partners, inconsistent condom use, or a previous STI. For men, there’s no universal screening recommendation yet, though testing is available and worth discussing with a provider if you’re at risk.
Damage to the Female Reproductive System
For women, untreated chlamydia poses the most serious long-term consequences. About 10 to 15% of women with untreated infections develop pelvic inflammatory disease (PID), a condition where the bacteria spread from the cervix into the uterus, fallopian tubes, or ovaries. PID causes inflammation that can scar the fallopian tubes, and that scarring can block eggs from reaching the uterus. The result can be chronic pelvic pain, difficulty getting pregnant, or ectopic pregnancy, where a fertilized egg implants outside the uterus and becomes a medical emergency.
What makes this especially concerning is that PID itself can also be subtle. Some women experience significant pain, but others have a low-grade version that causes damage without obvious symptoms. By the time fertility problems surface, the scarring may already be irreversible.
Repeat Infections Multiply the Risk
Getting chlamydia more than once dramatically raises the stakes. A study published in the American Journal of Obstetrics and Gynecology found that women with two chlamydia infections were twice as likely to be hospitalized for ectopic pregnancy and four times as likely to be hospitalized for PID compared to women with a single infection. Women with three or more infections faced even steeper odds: a 4.5 times greater risk of ectopic pregnancy and a 6.4 times greater risk of PID.
This happens because each round of infection triggers a new wave of inflammation in tissue that may already be partially scarred. The cumulative effect is what drives the most severe outcomes. Getting treated quickly the first time matters, but avoiding reinfection matters just as much. That means your sexual partners need treatment too, even if they feel fine.
Risks for Men
Chlamydia is generally less dangerous for men, but it’s not harmless. The most common complication is epididymitis, a painful inflammation of the tube that stores and carries sperm from the testicle. Symptoms include swelling, tenderness, and pain in one or both testicles. Left untreated, epididymitis can lead to chronic pain and, in some cases, reduced fertility.
Men can also develop reactive arthritis, a condition where the immune response to the infection triggers joint pain, eye inflammation, and urinary symptoms that persist even after the bacteria are cleared. This is uncommon but can be debilitating when it occurs.
Risks During Pregnancy and for Newborns
Chlamydia during pregnancy creates risks for both parent and baby. Untreated infection can increase the chance of preterm delivery and low birth weight. During vaginal delivery, the bacteria can pass to the newborn. Data from before routine prenatal screening showed that up to 60% of newborns born to infected mothers acquired the infection. Of those, roughly 30% developed eye infections (conjunctivitis) appearing 5 to 14 days after birth, and about 15% developed pneumonia.
These numbers are much lower today because pregnant women are routinely screened and treated. But the stakes underscore why prenatal chlamydia testing is standard practice. Neonatal eye infections from chlamydia can range from mild discharge to severe swelling with membrane formation, and they require systemic antibiotics rather than just eye drops, since at least half of affected newborns also carry the bacteria in their throat.
Connection to HIV Risk
Having chlamydia increases your chances of acquiring or transmitting HIV. The inflammation chlamydia causes in genital tissue makes it easier for HIV to enter the body during sexual contact. This is true for any active STI that causes inflammation or sores, but it’s particularly relevant for chlamydia given how widespread and often undetected it is.
How Easily It’s Cured
The good news is that chlamydia is highly curable with a short course of antibiotics. The current first-line treatment is a week-long course of doxycycline, which has proven more effective than the older single-dose alternative, particularly for rectal infections. One clinical trial found doxycycline achieved a 100% cure rate for rectal chlamydia, compared to 74% for the single-dose option. For standard genital infections in women, both treatments work well, though doxycycline is now preferred across the board.
Antibiotic resistance has not become a significant problem for chlamydia the way it has for gonorrhea. Treatment failures are rare when the full course is completed. The bigger issue is reinfection from an untreated partner, which is why both you and your partner need to be treated before resuming sexual contact. Most guidelines recommend retesting about three months after treatment to catch any reinfection early.
Who Should Get Tested
Testing is simple. A urine sample or a swab (which you can often collect yourself) is all that’s needed. Results typically come back within a few days. You should consider testing if you’re sexually active and fall into any of these categories:
- Women under 25: Annual screening is recommended regardless of symptoms or perceived risk.
- Women 25 and older with risk factors: A new partner, multiple partners, a partner with an STI, inconsistent condom use, or a previous STI all warrant screening.
- Men with symptoms or risk factors: While universal screening isn’t formally recommended for men, testing is straightforward and worthwhile if you have new or multiple partners.
- Pregnant women: Screening is standard at the first prenatal visit.
- Anyone with a known exposure: If a partner tests positive, get tested and treated regardless of symptoms.
Chlamydia is not dangerous in the way that makes headlines. It won’t put you in the hospital overnight. Its danger is slower and quieter: months of invisible infection that chip away at your fertility or set you up for complications you won’t discover until years later. The gap between how easy it is to treat and how much damage it can do when ignored is what makes it worth taking seriously.