Untreated chlamydia can cause permanent damage to your reproductive system, including scarring that leads to infertility, chronic pelvic pain, and dangerous pregnancy complications. Because 75% of women and 50% of men with chlamydia have no symptoms at all, the infection often progresses silently for months or even years before the damage becomes apparent.
Why Chlamydia Often Goes Untreated
The biggest reason chlamydia causes so much harm is that most people don’t know they have it. Without symptoms like unusual discharge, burning during urination, or pelvic pain, there’s no obvious signal to get tested. The bacteria can quietly persist in the reproductive tract, and in some people, it migrates upward from the initial site of infection (the cervix in women, the urethra in men) into deeper reproductive organs. There, it can establish a chronic infection while triggering an inflammatory response that slowly scars the surrounding tissue.
This is why the CDC recommends annual chlamydia screening for all sexually active women under 25, and for older women with risk factors like new or multiple partners. Men who have sex with men should also be screened at least annually. Routine screening is the primary way chlamydia gets caught early enough to prevent complications.
Complications in Women
The most serious consequence for women is pelvic inflammatory disease (PID), an infection that spreads to the uterus, fallopian tubes, or ovaries. PID develops in 10% to 40% of women with untreated chlamydia. It can cause intense lower abdominal pain, fever, and abnormal bleeding, but it can also be surprisingly mild or even painless, meaning some women don’t realize it’s happening until the damage is done.
PID causes inflammation and scarring inside the fallopian tubes. That scarring can partially or fully block the tubes, which has two major consequences. First, it can prevent sperm from reaching an egg, causing tubal factor infertility. A large prospective study published in The Lancet Regional Health found that women who tested positive for chlamydia had roughly 2.8 times the risk of tubal factor infertility compared to women who never had the infection. Second, a partially blocked tube can trap a fertilized egg, leading to an ectopic pregnancy, where the embryo implants outside the uterus. This is a medical emergency. The same study found that chlamydia nearly doubled the risk of ectopic pregnancy.
Women who have had PID also face a higher chance of chronic pelvic pain that can persist long after the infection itself is treated. The scarring and adhesions left behind don’t reverse on their own.
Complications in Men
In men, untreated chlamydia most commonly leads to epididymitis, an infection of the coiled tube behind the testicle that stores and carries sperm. It causes pain, swelling, and tenderness in one or both testicles, and the inflammation can spread from the epididymis into the testicle itself, a condition called epididymo-orchitis. The spermatic cord often becomes swollen and painful as well.
If epididymitis isn’t treated, it can lead to chronic testicular pain and, in some cases, reduced fertility. Scarring in the epididymis can obstruct the passage of sperm. While male infertility from chlamydia is less common than female infertility from the same infection, it does happen, and it’s preventable with early treatment.
Men can also develop urethritis (inflammation of the urethra) that causes discharge and discomfort during urination, though this is often the symptom that brings men in for testing before deeper complications develop.
Joint Inflammation From Chlamydia
Chlamydia doesn’t only affect the reproductive system. In roughly 4% to 8% of people with a chlamydial infection, the immune system’s response to the bacteria triggers reactive arthritis, a condition that causes painful swelling in the joints, particularly the knees, ankles, and feet. It can also cause inflammation in the eyes and urinary tract.
Reactive arthritis typically appears weeks after the initial infection. For most people it resolves within several months, but some develop a chronic form that causes recurring joint pain and stiffness. The condition is diagnosed by detecting chlamydia or its components at the original infection site or, in more specific testing, in the joint fluid itself.
Risks During Pregnancy
Chlamydia during pregnancy poses risks to both the mother and the baby. Beyond the increased chance of ectopic pregnancy, an active infection at the time of delivery can be passed to the newborn during birth. This can cause eye infections (neonatal conjunctivitis) and pneumonia in the baby.
Because of these risks, the CDC recommends chlamydia testing for all pregnant women under 25, with retesting during the third trimester. Pregnant women who test positive should have a follow-up test four weeks after treatment and again within three months to confirm the infection has cleared.
How Quickly Damage Occurs
There’s no precise timeline for when untreated chlamydia crosses the line from a simple infection to permanent damage. The progression varies from person to person and depends on factors like immune response, whether reinfection occurs, and which part of the reproductive tract is affected. What’s clear is that the longer the infection persists, the greater the risk. An infection left untreated for years carries a significantly higher chance of PID, scarring, and infertility than one caught within weeks or months.
The good news is that chlamydia itself is easy to cure with antibiotics when it’s caught early. The infection typically clears within one to two weeks of treatment. But the scarring and structural damage it leaves behind in the fallopian tubes, epididymis, or joints cannot be reversed by antibiotics. That’s what makes early detection so important: treating the infection is simple, but undoing its complications is not.
Reinfection After Treatment
Getting treated once doesn’t protect you from getting chlamydia again. Reinfection rates are high: one study tracking patients after treatment found that about 17% tested positive again within six months. Each new infection restarts the cycle of inflammation and increases the cumulative risk of scarring and complications.
This is why the CDC recommends retesting roughly three months after treatment. Your sexual partners also need to be treated at the same time, or the infection will simply pass back and forth between you. Using condoms consistently and getting screened regularly are the most reliable ways to prevent reinfection and the long-term damage that comes with it.