Chlamydia doesn’t have formally defined “stages” the way syphilis does, but the term “late stage” generally refers to the complications that develop when a chlamydia infection goes untreated for months or longer. Because chlamydia is silent in most people (up to 70% of women and 50% of men have no symptoms at all), infections can persist for over a year without detection. During that time, the bacteria can spread beyond the initial infection site and cause scarring, inflammation, and organ damage that may be permanent even after the infection itself is cured.
How Long It Takes for Complications To Develop
The average untreated chlamydia infection in women lasts more than a year. Mathematical modeling published in BMC Infectious Diseases estimates that it takes roughly 228 to 253 days before half of the expected cases of pelvic inflammatory disease (PID) develop from an untreated infection. That means complications don’t typically appear in the first few weeks. Instead, the bacteria gradually ascend from the cervix or urethra into deeper tissues over many months, giving screening a meaningful window to catch and treat the infection before damage occurs.
About 5% of untreated chlamydia infections cause PID in the first few weeks, but within a year, that number climbs to roughly 9.5%. If gonorrhea is present at the same time, the risk of PID jumps to around 30%.
Complications in Women
The most significant long-term damage from chlamydia in women centers on the reproductive system. PID is the hallmark complication: the bacteria travel up through the uterus and into the fallopian tubes, causing inflammation that can scar the tissue. This scarring narrows or blocks the tubes, which creates two major problems. First, it can prevent eggs from reaching the uterus, leading to infertility. Second, a fertilized egg may implant inside the damaged tube rather than the uterus, causing an ectopic pregnancy, a potentially life-threatening emergency.
Among women who develop PID, 15 to 20% go on to experience infertility. Repeated chlamydia infections compound the damage, with each episode adding more scarring. Chronic pelvic pain is another common outcome, caused by adhesions (bands of scar tissue) that form between pelvic organs. Some women live with this pain for years after the infection has been treated.
Imaging can reveal the extent of internal damage. Ultrasound may show fluid-filled fallopian tubes (hydrosalpinx), thickened tube walls, or abscesses near the ovaries. In some cases, a procedure called laparoscopy, where a small camera is inserted through the abdomen, is used to directly visualize scarring and adhesions.
Complications in Men
In men, untreated chlamydia most commonly spreads to the epididymis, the coiled tube behind each testicle that stores and carries sperm. This condition, called epididymitis, causes one-sided testicular pain, swelling, and tenderness that can extend to the spermatic cord. It sometimes develops alongside urethritis, which itself may produce no noticeable symptoms.
If epididymitis goes untreated or recurs, it can lead to chronic pain and, in some cases, reduced fertility due to scarring of the sperm-carrying ducts. Chlamydia can also cause inflammation of the prostate gland, leading to discomfort in the pelvic area, pain during urination, or pain during ejaculation.
Reactive Arthritis
One of the more surprising complications of long-standing chlamydia is reactive arthritis, a condition where the immune system’s response to the infection triggers inflammation in the joints. Chlamydia is the cause in roughly two-thirds of sexually acquired reactive arthritis cases.
The condition typically targets the knees, ankles, and feet with asymmetric joint pain, swelling, and morning stiffness. But it can affect far more than the joints. Between 20 and 40% of people with this condition develop painful inflammation where tendons attach to bone, particularly in the heels and feet, making walking difficult. About 30% experience eye irritation or conjunctivitis. Skin symptoms are also common: a scaly, psoriasis-like rash appears in roughly 12% of cases, and painful sores on the soles of the feet develop in 5 to 33%. Some patients also report fatigue, weight loss, and fever.
Risks During Pregnancy and to Newborns
Untreated chlamydia during pregnancy poses serious risks to the baby during delivery. An estimated 50 to 70% of infants born to mothers with active genital chlamydia become infected as they pass through the birth canal. Of those exposed infants, 30 to 50% develop conjunctivitis (an eye infection that can damage the cornea if untreated) and 10 to 20% develop pneumonia in the first months of life. Studies from clinical settings have found chlamydia-associated pneumonia rates as high as 51% among colonized newborns evaluated with chest X-rays.
Lymphogranuloma Venereum: A More Aggressive Form
A specific set of chlamydia strains (called L1, L2, and L3) cause a condition known as lymphogranuloma venereum, or LGV, which is genuinely staged and far more aggressive than typical chlamydia. It begins with a small, painless genital ulcer or bump at the site of infection that often goes unnoticed. Within weeks, the infection moves into nearby lymph nodes, causing painful, swollen lumps in the groin that can rupture and drain pus.
When LGV affects the rectum, which is common among men who have sex with men, it causes severe proctocolitis: bloody discharge, intense rectal pain, constipation, and fever. The symptoms can closely mimic inflammatory bowel disease. Left untreated, LGV can lead to chronic colorectal fistulas (abnormal tunnels between the bowel and other structures) and permanent narrowing of the rectum from scar tissue.
Can the Damage Be Reversed?
The infection itself is easily cured with a week-long course of antibiotics. But the damage it leaves behind is a different story. Scarring in the fallopian tubes, adhesions in the pelvis, and structural changes from chronic inflammation do not resolve once the bacteria are cleared. There is no medication that reverses internal scarring.
The picture for fertility, however, isn’t entirely bleak. Research on women with a history of chlamydia who underwent assisted reproduction found that, after treatment, those without fluid-filled tubes (hydrosalpinx) had clinical pregnancy and live birth rates comparable to women who had never been infected. The main difference was that women with prior chlamydia infections took longer to conceive naturally, likely because of minor tubal damage that slows the egg’s journey without blocking it entirely.
For reactive arthritis, the joint inflammation typically improves over weeks to months once the underlying infection is treated, though a subset of people develop recurring or chronic symptoms. Chronic pelvic pain from adhesions can sometimes be managed with physical therapy or, in severe cases, surgery to remove scar tissue, though adhesions tend to re-form.
The core problem with “late stage” chlamydia is that most of the damage happens silently. By the time symptoms appear, whether that’s pelvic pain, difficulty getting pregnant, or joint inflammation, the infection has often been present for many months. This is why routine screening, particularly for sexually active women under 25, catches infections before they have a chance to cause lasting harm.