Sexual health

What Untreated Chlamydia Does to the Body

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Chlamydia is called a silent infection for good reason: most people who have it never notice, which gives the bacteria weeks or months to move beyond where it started. Left alone, it can scar the fallopian tubes, set up a tubal pregnancy, or leave a man with a swollen, aching epididymis — all from an infection that a course of antibiotics would have cured completely.

Last updated: July 2026

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Why Chlamydia Goes Untreated So Often

Chlamydia is the most commonly reported bacterial sexually transmitted infection in the United States, and the reason it so often goes untreated has little to do with access to care: most people who have it have no symptoms at all, so there is nothing prompting a visit to a clinician in the first place 1. More than 1.6 million cases were reported in 2023, out of over 2.4 million combined chlamydia, gonorrhea, and syphilis cases nationwide, and nearly half of all those cases were in people ages 15 to 24 2.

Chlamydia is frequently described as 'silent' because most infections cause no noticeable symptoms 1. That is exactly why the U.S. Preventive Services Task Force recommends annual chlamydia and gonorrhea screening for all sexually active women 24 and younger, and for older women at increased risk 3 — waiting for symptoms misses the majority of infections, and it's in the gap between infection and diagnosis where complications have time to develop.

In Women: Pelvic Inflammatory Disease, Scarring, and Ectopic Pregnancy

An untreated chlamydia infection can travel out of the cervix and upward into the uterus, fallopian tubes, and ovaries, causing pelvic inflammatory disease — an infection of the upper reproductive tract and one of the most serious preventable consequences of an untreated STI 1. The scar tissue this inflammation leaves behind in the fallopian tubes is a leading cause of infertility, and it can also cause an ectopic pregnancy, where a fertilized egg implants outside the uterus, usually in a scarred tube, in a pregnancy that cannot continue safely.

Pelvic inflammatory disease does not always cause severe symptoms — it can do lasting damage while feeling like only mild pelvic discomfort, or nothing at all. How pelvic inflammatory disease feels varies enormously from one person to the next, which is part of why it is so often missed until a fertility evaluation years later traces the scarring back to an infection nobody knew was there.

In Men: Epididymitis and Testicular Pain

In men, an untreated chlamydia infection can spread from the urethra into the epididymis, the coiled tube behind each testicle that stores and carries sperm, causing epididymitis — pain, swelling, and tenderness usually on one side, sometimes with a low fever. It typically responds well to antibiotics once diagnosed, and lasting fertility effects in men are far less common than the damage untreated chlamydia can cause in women, though the pain itself can be severe enough to send someone to urgent care before any STI is suspected.

Sudden, severe testicular pain is never something to wait out, whether or not chlamydia turns out to be the cause: it can also signal testicular torsion, a twisting of the testicle that cuts off its blood supply and is a true emergency handled surgically, not with antibiotics. An exam is the only way to tell the two apart quickly enough to matter.

It Rarely Travels Alone

Chlamydia and gonorrhea are frequently transmitted together, and gonorrhea carries a strikingly similar list of complications: it can also infect the genitals, rectum, or throat, often without symptoms, and left untreated it can cause the same pelvic inflammatory disease, ectopic pregnancy risk, and infertility that chlamydia does 4. Because the two infections look identical on a symptom checklist and are tested for from the same swab or urine sample, a clinician diagnosing one usually tests for the other automatically rather than assuming a single infection explains everything.

Gonorrhea's trend in recent years has moved in a different direction than syphilis — overall case counts have started to decline even as syphilis has surged 2 — but that decline does not change the practical advice for anyone diagnosed with chlamydia: a full STI panel, not a single test, is what actually rules out the infections that share its complications.

Why the Partner Needs Treatment Too

Chlamydia is easy to pass back and forth between partners, and treating only the person who was tested leaves the door open for reinfection almost immediately. Reinfection is common enough that clinicians routinely offer expedited partner therapy, delivering medication or a prescription for a partner to take without requiring that partner to be examined first, when a partner from the past 60 days is unlikely to seek timely care of their own 5. Expedited partner therapy exists specifically to close this gap, since an infection treated in only one partner is very likely to simply pass back after sex resumes.

Waiting to have sex again until both partners have completed treatment, not just until symptoms — if there were any — resolve, is what actually breaks the cycle. A course of antibiotics cures chlamydia completely, but only if it reaches every person carrying the infection, not just the one who happened to get tested first.

Testing and Treatment Stop All of This

Chlamydia is fully curable with a short course of antibiotics, and treatment is what actually prevents every complication described above — the damage comes from the infection being present and active in the body over time, not from chlamydia itself being especially dangerous once it is found and treated 1. That makes testing, not symptoms, the thing that matters most: sexually active women 24 and younger are advised to be screened for chlamydia and gonorrhea annually regardless of symptoms, along with other groups at increased risk 3.

Chlamydia is one of the most straightforward STIs to cure — a short course of antibiotics clears it completely. The complications described here are what happens when that straightforward cure doesn't happen soon enough, which is the entire argument for testing on a schedule rather than waiting to feel like something is wrong.

Common questions

There's no fixed timeline — some people develop pelvic inflammatory disease within weeks of infection, while others carry it silently for months or longer before any complication shows up. That unpredictability is exactly why testing on a regular schedule, rather than waiting for a specific number of weeks to pass, is the more reliable approach.

Antibiotics will cure the chlamydia infection itself at any point it's diagnosed, but they can't undo scar tissue that has already formed in the fallopian tubes or elsewhere. That's the practical difference between the infection and its complications: one is always curable, the other is sometimes not reversible.

No. Many people with untreated chlamydia never develop pelvic inflammatory disease, and clinicians can't currently predict who will and who won't. The risk rises the longer an infection goes untreated and with repeated infections over time, which is part of why treating every infection promptly matters even when the odds of complications feel low.

Yes, though less often than the complications seen in women. Untreated chlamydia in men can cause epididymitis, an inflamed, painful, swollen epididymis, and can sometimes affect fertility, though this is less common than the fallopian tube damage untreated chlamydia can cause in women.

Yes. Treating only one partner while the other stays untreated makes reinfection likely almost as soon as sex resumes. Many clinicians can provide expedited partner therapy — medication or a prescription for a partner to take without an exam of their own — specifically to close this gap quickly.

The same infection doesn't relapse once properly treated with antibiotics, but a new infection can happen anytime after future exposure, including from an untreated partner. That's why repeat testing a few months after treatment is often recommended, particularly when a partner's treatment status is uncertain.

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When Pelvic or Testicular Pain Needs Same-Day Care

  • —Severe lower abdominal or pelvic pain, especially with fever, nausea, or vomiting
  • —Any new pelvic pain or vaginal bleeding during pregnancy
  • —Sudden, severe pain and swelling in one testicle
  • —Pelvic pain severe enough to interfere with walking or daily activity

Severe abdominal or pelvic pain with fever, or sudden one-sided testicular pain and swelling, warrants same-day medical care or an emergency room visit — the second is checked emergently to rule out testicular torsion, a time-sensitive condition unrelated to infection that still needs the same fast evaluation.

This article is educational and does not replace an in-person evaluation. A clinician can test for chlamydia and related infections, treat it, and check for complications like pelvic inflammatory disease or epididymitis.

References

  1. 1.Centers for Disease Control and Prevention (2024). About Chlamydia. CDC (cdc.gov/chlamydia). linkUsed to support that chlamydia is a common, curable bacterial STI that is frequently asymptomatic, can cause pelvic inflammatory disease and infertility in women if untreated, and is treated with antibiotics.
  2. 2.Centers for Disease Control and Prevention (2025). National Overview of STIs in 2023. CDC STI Statistics (Sexually Transmitted Infections Surveillance, 2023). linkUsed to support 2023 U.S. surveillance figures on chlamydia case counts, the concentration of cases among people ages 15-24, and the recent decline in gonorrhea and syphilis case trends.
  3. 3.US Preventive Services Task Force (2021). Chlamydia and Gonorrhea: Screening. US Preventive Services Task Force (final recommendation, JAMA 2021). link ✓Used to support the Grade B recommendation to screen for chlamydia and gonorrhea in sexually active women 24 and younger, and in women 25+ at increased risk.
  4. 4.Centers for Disease Control and Prevention (2024). About Gonorrhea. CDC (cdc.gov/gonorrhea). linkUsed to support that gonorrhea shares chlamydia's pattern of frequent asymptomatic infection and can cause the same pelvic inflammatory disease, ectopic pregnancy risk, and infertility if untreated.
  5. 5.Centers for Disease Control and Prevention (2021). Expedited Partner Therapy. CDC STI Treatment Guidelines, 2021. linkUsed to support that expedited partner therapy is routinely offered for chlamydia so a patient's recent partners can be treated without requiring their own exam first, reducing reinfection.

5 sources, numbered by first appearance. General health information, not medical advice. AI-assisted editorial content — citations link their sources. Editorial policy

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