Chlamydia trachomatis

Most people who carry this infection have no idea they have it. More than 70% of infected women and more than 80% of infected men have no symptoms at all, yet untreated infection is a leading cause of pelvic infections, blocked fallopian tubes, and infertility. A urine test lets you find out without an exam or a swab.

Because it is so quiet, testing is the only reliable way to know whether you carry it. This version uses a urine sample you can provide yourself, which is why it has become the backbone of large screening programs.

What This Test Detects

This test looks for Chlamydia trachomatis (the bacterium behind the sexually transmitted infection most people just call chlamydia) by copying and detecting its genetic material in your urine. The lab method, called a nucleic acid amplification test or NAAT, is highly sensitive and can detect very small amounts of bacterial genetic material that older culture or antigen tests would miss.

The result is a yes or no answer, not a level on a scale. A positive result means the bacterium's genetic material was found, signaling a current infection. A negative result means none was detected. It reflects an active infection right now, not a past one you already cleared.

Pelvic Inflammatory Disease and Infertility

The reason this infection matters is that, untreated, it can travel upward and damage the reproductive organs. In a long-term study of women, those who tested positive developed a deep infection of the uterus and tubes (pelvic inflammatory disease, or PID) at roughly three times the rate of those who tested negative (4.4 versus 1.4 per 1,000 women each year).

Over years of follow-up, women with a chlamydia history carried meaningfully higher risks: about 60% higher risk of PID, roughly 1.8 times the risk of a pregnancy that implants outside the womb (an ectopic pregnancy), and about 2.8 times the risk of scarring that blocks the fallopian tubes (tubal factor infertility). The absolute number of women affected stayed low, but the increase in risk was real and consistent.

Symptoms seem to signal more danger, not less. Among chlamydia-positive women, those with symptoms had close to three times the PID risk of those without. Being infected young also mattered, with the highest tubal-scarring risk in women first infected before age 20.

One nuance is worth knowing. Some evidence, including antibody studies that measure past exposure rather than current urine infection, links prior infection more strongly to long-term damage than a single current positive urine test does. A positive result is a signal to treat and follow up, and the harm comes mainly from infections that go undetected and untreated over time.

Pregnancy and Newborn Risks

In pregnancy, infection detected from a urine sample has been tied to early delivery. In a population study of pregnant women, chlamydia was linked to about four times the risk of delivering before 32 weeks and roughly two and a half times the risk of delivering before 35 weeks. Reported harms also include newborn eye and lung infections.

The pregnancy evidence is not uniform. A larger population-based study found no clear link to poor birth outcomes after accounting for other factors, so this association remains contested. The practical takeaway is that finding and treating infection early in pregnancy is the point, and a urine test makes that easy.

Why the Specimen You Give Matters

For men, urine is the preferred sample, and modern tests catch nearly every infection, with sensitivity around 93% to 100% and very few false alarms. If you are a man, a urine test is close to the best you can do noninvasively.

For women, urine is useful but not the strongest choice. Pooled data across many studies found urine caught about 87% of infections in women, while a self-collected vaginal swab caught about 94%. That gap means a negative urine result in a woman does not fully rule out infection, and a vaginal swab is the more reliable specimen when it is an option.

Urine also only samples the lower genital tract. It will not detect infection in the rectum or throat, which can matter for anyone with those exposures. If exposure at those sites is possible, urine testing alone is not enough.

Why One Test Is Not Enough

A single result is a snapshot of one moment. Because reinfection from an untreated partner is common, this test earns most of its value from repeat use over time rather than from any one reading.

Two habits make the difference. First, a follow-up test after treatment. In a study of pregnant women treated with a single dose of azithromycin, nearly 1 in 4 still had chlamydia detected later, from either persistence or reinfection, so confirming clearance is not optional. Second, rescreening about three months after any positive result, since re-catching the infection from a partner is the most common outcome. If you are a sexually active woman aged 24 or younger, or have new partners, at least annual testing is the sensible baseline, not a stretch.

When Results Can Be Misleading

The most common way to be misled is a false negative in specific situations:

• Female urine sensitivity: urine misses more infections in women than a vaginal swab does, so a negative urine result is less reassuring than a negative swab.
• Very low bacterial load: early or low-level infections sit near the test's detection limit, where results can flip between assays, and some genetic-based tests outperform others at low levels.
• Sample handling: freezing and certain storage or collection errors have produced false negatives in a share of urine samples.
• Rare escape variants: uncommon bacterial mutants can dodge the specific target some tests look for, producing a negative result despite true infection.

False positives are less common because these tests are highly specific, typically clearing more than 98 out of 100 uninfected people correctly. When they happen, it is usually a weak, low-level signal near the test's decision threshold, which is why labs often repeat borderline results before acting on them. Recent antibiotics can also suppress or clear detectable material, so testing too soon after treatment can mislead.

What to Do With an Unexpected Result

A positive result has a clear pathway. Get treated with the recommended antibiotics, make sure recent partners are notified and treated so you are not immediately reinfected, and plan a rescreen about three months later. Because coinfection is common, a positive chlamydia result is also a reason to test for gonorrhea, trichomonas, HIV, and syphilis if you have not already.

A negative result that conflicts with your situation deserves a second look. If you are a woman with symptoms or a known exposure, a self-collected vaginal swab is more sensitive than urine and is the better next step. If you have had rectal or throat exposure, ask about testing those sites directly, since urine cannot sample them. A clinician can help match the specimen and the panel to your actual exposures.