Untreated chlamydia can turn into several serious health problems, including pelvic inflammatory disease, chronic pain, infertility, and joint inflammation. Because chlamydia often causes no symptoms at all, many people carry the infection for months without knowing it, giving it time to spread deeper into the reproductive tract and, in some cases, trigger immune reactions throughout the body.
Pelvic Inflammatory Disease
The most common and consequential progression of untreated chlamydia in women is pelvic inflammatory disease, or PID. This happens when the bacteria travel upward from the cervix into the uterus, fallopian tubes, and surrounding tissue, causing inflammation and scarring. PID can develop silently or cause noticeable symptoms like lower abdominal pain, pain during sex, unusual vaginal discharge, and bleeding between periods.
The real danger of PID is the lasting damage it leaves behind. Scar tissue in the fallopian tubes can block eggs from reaching the uterus, leading to infertility or ectopic pregnancy, where a fertilized egg implants outside the womb. Ectopic pregnancies are medical emergencies. Even after PID is treated with antibiotics, the scarring it caused doesn’t reverse, so the fertility consequences can be permanent. Some women develop chronic pelvic pain that persists long after the infection clears.
Epididymitis in Men
In men, untreated chlamydia most commonly turns into epididymitis, an infection of the coiled tube behind each testicle that stores and carries sperm. Chlamydia and gonorrhea are the leading causes of epididymitis in sexually active young men. Symptoms include scrotal pain and swelling, usually on one side, along with pain during urination and sometimes a discharge.
Most cases respond well to antibiotics, but if the infection lingers or recurs, it can cause scarring in the reproductive tract. Reduced fertility is a recognized complication, though it’s considered rare. In severe cases, the infection can spread to the testicle itself, a condition called epididymo-orchitis, which is more painful and harder to treat.
Reactive Arthritis
Chlamydia can trigger an immune overreaction that attacks your joints, eyes, and urinary tract. This condition, called reactive arthritis, develops in an estimated 1 to 3 percent of people who have a chlamydia-related urethral infection. It’s not the bacteria themselves invading the joints. Instead, the immune system misfires after the initial infection and causes inflammation in unrelated parts of the body.
The classic pattern involves three symptoms appearing together: joint pain and swelling (often in the knees, ankles, or feet), eye redness or irritation, and urinary discomfort. In practice, only about one third of patients show all three symptoms at once. Many people develop just the joint inflammation, which can be severe enough to limit mobility. Some also get skin changes on the palms or soles. Reactive arthritis usually resolves within months, but it can become a chronic, recurring problem for some people.
Lymphogranuloma Venereum
Certain strains of the chlamydia bacterium cause a more aggressive infection called lymphogranuloma venereum, or LGV. Unlike typical chlamydia, which tends to be mild or silent, LGV causes severe inflammation and can become an invasive, systemic infection. It’s most commonly seen in men who have sex with men, though anyone can be affected.
When LGV affects the rectum, it causes proctocolitis, with symptoms that mimic inflammatory bowel disease: mucous or bloody rectal discharge, anal pain, constipation, fever, and a persistent feeling of needing to use the bathroom. When it enters through genital contact, it typically causes painful, swollen lymph nodes in the groin, sometimes severe enough to form large abscesses called buboes. Left untreated, rectal LGV can lead to chronic fistulas and strictures, meaning permanent narrowing and abnormal connections in the bowel.
Increased Risk of HIV
Having chlamydia makes you significantly more vulnerable to HIV if you’re exposed. The inflammation chlamydia causes in genital and rectal tissue brings immune cells to the surface and disrupts the protective lining, creating easier entry points for the virus. The presence of a sexually transmitted infection can amplify HIV transmission risk by as much as eight times. This works both ways: if you already have HIV, a concurrent chlamydia infection can also make you more likely to pass HIV to a partner.
Risks to Newborns
Chlamydia can pass from mother to baby during vaginal delivery, and the consequences for newborns are significant. Before routine screening of pregnant women became standard, up to 60 percent of babies born to infected mothers acquired the infection. Of those, roughly 30 percent developed conjunctivitis, an eye infection that causes swelling, redness, and discharge in the first few weeks of life. About 15 percent developed chlamydial pneumonia, a lung infection that typically appears between one and three months of age.
At least half of newborns with chlamydial eye infections also carry the bacteria in their nasal passages, which is the pathway to pneumonia. This is why newborns with chlamydial conjunctivitis are treated with oral antibiotics rather than just eye drops. Screening pregnant women and treating the infection before delivery prevents these complications almost entirely.
Who Should Get Screened
Because chlamydia so often causes no symptoms, screening is the main tool for catching it before it causes damage. Current CDC guidelines recommend annual chlamydia testing for all sexually active women under 25 and for women 25 and older who have risk factors like a new partner, multiple partners, or a partner with an STI. Pregnant women should be screened early in pregnancy, with retesting in the third trimester for those under 25 or at higher risk.
For men who have sex with men, annual screening at all sites of sexual contact is recommended regardless of condom use. Those on HIV prevention medication, living with HIV, or with multiple partners should test every three to six months. There’s no blanket screening recommendation for heterosexual men at low risk, though screening may be offered in high-prevalence settings like STI clinics or correctional facilities. Transgender and gender diverse individuals should be screened based on their anatomy and sexual practices.
Anyone who tests positive and gets treated should retest about three months later. Reinfection is common, especially if a partner wasn’t treated at the same time, and each new infection carries the same risk of progressing into the complications above.