Yes, chlamydia gets worse over time. The infection does not resolve on its own, and the longer it goes untreated, the more likely it is to spread from the initial infection site into deeper parts of the reproductive system, where it can cause scarring, chronic pain, and fertility problems. What makes this particularly risky is that roughly 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 realizes it’s there.
Why Chlamydia Spreads Without You Knowing
Chlamydia typically starts in the cervix in women or the urethra in men. In the early stages, it often causes no noticeable symptoms. When symptoms do appear, they can take several weeks after exposure to show up, and even then they’re often mild enough to dismiss: unusual discharge, a slight burning during urination, or minor pelvic discomfort.
The bacteria itself doesn’t have any built-in ability to move through the body. Instead, your own immune system inadvertently helps it spread. When immune cells attack the infected tissue, they detach infected cells from the lining of the reproductive tract. Those detached cells, still carrying live bacteria, get carried upward by the natural muscular contractions of the uterus. Research published in PLOS Computational Biology found that the timing of this process relative to the menstrual cycle, the strength of the immune response, and the amount of bacteria present all influence whether the infection stays localized or climbs into the upper reproductive tract. In modeling simulations, about 36% of infections ascended beyond the cervix.
How Untreated Chlamydia Damages the Reproductive System
The most significant risk for women is pelvic inflammatory disease (PID), an infection of the uterus, fallopian tubes, or ovaries. A large evidence synthesis estimated that about 17% of women with untreated chlamydia will develop PID, including cases that are never formally diagnosed. Even among cases that would be caught in a clinical setting, the rate sits around 15%.
PID matters because it creates scar tissue. When the fallopian tubes become scarred, they can partially or fully block the path an egg takes to reach the uterus. This leads to three possible outcomes, all serious:
- Infertility. Scar tissue in the fallopian tubes is one of the leading structural causes of difficulty conceiving. Research estimates that chlamydia accounts for roughly 11 to 26% of tubal factor infertility cases, depending on the population studied.
- Ectopic pregnancy. A fertilized egg can implant in a damaged fallopian tube instead of the uterus. This is a medical emergency that can cause life-threatening bleeding.
- Chronic pelvic pain. Ongoing inflammation and scarring can cause persistent abdominal and pelvic pain that lasts long after the original infection is gone.
None of these complications happen overnight. They develop gradually as the infection persists and the body’s repeated inflammatory responses cause cumulative tissue damage. A single untreated infection carries real risk, but repeated infections multiply it substantially.
Complications in Men
Men face fewer long-term consequences overall, but chlamydia is not harmless for them either. The infection can spread from the urethra to the epididymis, the coiled tube behind each testicle where sperm mature. Chlamydia is responsible for an estimated 40 to 80% of epididymitis cases. This causes pain, swelling, and fever, and in some cases can lead to orchitis (inflammation of the testicle itself) or prostatitis.
The impact on fertility in men is real but more variable. Research has shown that active chlamydia infection can reduce sperm concentration, decrease motility, damage sperm DNA, and increase the number of non-viable sperm. One study of asymptomatic infertile men found that those who tested positive for chlamydia and then received antibiotic treatment saw improvements of over 57% in most sperm quality measures within 30 days. That said, some studies have found no significant impact on semen quality, so the effect likely depends on how long the infection has been present and how far it has spread.
Risks During Pregnancy
Untreated chlamydia during pregnancy increases the risk of preterm delivery and low birth weight. The infection can also pass to the baby during vaginal delivery, potentially causing eye infections or pneumonia in the newborn. This is why routine chlamydia screening is standard in prenatal care.
Effects Beyond the Reproductive System
In a small number of people, chlamydia triggers reactive arthritis, a condition that causes joint pain, swelling, and inflammation in the eyes or urinary tract. This happens when the immune system overreacts to the infection and begins attacking the body’s own tissues. Most people infected with chlamydia will never develop this, but it’s a recognized complication. Untreated chlamydia also appears to increase susceptibility to HIV transmission.
Treatment Is Simple, but Timing Matters
The standard treatment is a seven-day course of an antibiotic taken twice daily. An alternative single-dose option also exists. Treatment itself is straightforward, effective, and clears the active infection. What it cannot do is reverse scarring or structural damage that has already occurred. This is what makes early detection so important: the infection is easy to cure, but the complications it causes over time are not.
Because most cases produce no symptoms, routine screening is the most reliable way to catch chlamydia before it progresses. Sexually active women under 25, anyone with new or multiple partners, and pregnant women are all groups where regular testing has the highest payoff. If you’ve been treated for chlamydia, retesting about three months later is recommended, since reinfection is common and restarts the clock on potential damage.