Lab result explainedInflammationLast updated November 11, 2026

Chlamydia test: how it works, how accurate urine and swab tests are, and what positive and negative results mean

Chlamydia test · Chlamydia trachomatis / Neisseria gonorrhoeae NAAT (CT/NG), urine or swab · reported in Qualitative: negative (not detected) or positive (detected); some reports add 'equivocal' or 'invalid'. No numeric value

A chlamydia test looks for the bacterium Chlamydia trachomatis, the most commonly reported bacterial sexually transmitted infection in the United States, with about 1.6 million cases reported each year and many more undiagnosed. Modern testing uses a nucleic acid amplification test (NAAT), which detects the organism's DNA or RNA in a first-catch urine sample or a swab from the vagina, cervix, urethra, rectum or throat. The result is simply negative (not detected) or positive (detected); there is no number to interpret.

The test is highly accurate when the right sample is collected at the right time. NAATs detect roughly 92 to 98 percent of infections (a self-collected vaginal swab is the most sensitive sample in women, first-catch urine the standard in men) and give a false positive in fewer than 1 in 100 tests. Because about 70 percent of women and half of men with chlamydia have no symptoms, screening is how most infections are found: the CDC and US Preventive Services Task Force recommend yearly testing for all sexually active women under 25, for older women with new or multiple partners, for pregnant women, and at every exposed site for men who have sex with men.

Results from a laboratory usually take 1 to 3 days; point-of-care NAATs available in some clinics give an answer in about 30 minutes. A positive test is fully treatable with a short course of antibiotics, partners from the previous 60 days are tested and treated, and everyone is retested about 3 months later because reinfection is common. Testing too soon after an exposure (under 1 to 2 weeks) or too soon after treatment (under 3 to 4 weeks) is the main source of misleading results.

Chlamydia test at a glance

  • What it is: a NAAT (PCR-type test) for Chlamydia trachomatis DNA or RNA in first-catch urine or a swab; usually run together with the gonorrhea test on the same sample.
  • Normal: negative (not detected). Reliable if collected at least 1 to 2 weeks after the last possible exposure; a negative taken earlier is repeated at 2 weeks.
  • Positive: chlamydia infection is present. It is fully treatable with antibiotics (the CDC's first-line regimen is 7 days of doxycycline); partners from the last 60 days need testing and treatment, and sex is avoided until 7 days after everyone has completed treatment.
  • Accuracy: sensitivity about 92 to 98 percent (vaginal swab highest, female urine lowest), specificity over 99 percent. Urine must be first-catch, not midstream, ideally at least 1 hour after you last urinated.
  • How long results take: 1 to 3 days from a laboratory, 30 to 90 minutes with a point-of-care NAAT, 2 to 5 days for mailed home-collection kits.
  • After treatment: do not retest in the first 3 to 4 weeks (DNA from dead bacteria can still be detected); everyone is retested at 3 months because 10 to 20 percent are reinfected.

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What Chlamydia test measures

A NAAT amplifies a target sequence unique to Chlamydia trachomatis, usually from its cryptic plasmid or ribosomal RNA, until it is detectable, which lets the test find as few as a handful of organisms in a sample. It detects genetic material from live and dead bacteria alike, which is why it is so sensitive and also why it can stay positive for a few weeks after successful treatment. Nearly all US laboratories run chlamydia and gonorrhea together on one sample (a CT/NG test), and some add Trichomonas vaginalis or Mycoplasma genitalium.

The sample matters more than the brand of test. In women, a vaginal swab (self-collected or clinician-collected, equally good) detects about 96 to 98 percent of infections, an endocervical swab about 95 percent, and first-catch urine about 85 to 93 percent, which is why guidelines prefer the swab. In men, first-catch urine (the first 20 to 30 mL, not midstream) detects 95 to 98 percent and is as good as a urethral swab. Rectal and throat swabs are FDA-cleared for the major assays and are far more sensitive than culture at those sites; a urine test does not detect rectal or throat infection.

Older methods (culture, antigen tests, DNA probes) missed 20 to 40 percent of infections and are no longer used for routine diagnosis. The incubation period is 7 to 21 days, and a NAAT can turn positive within days of exposure, but most guidance suggests testing at 2 weeks to avoid a false negative from a very early infection. Mailed self-collection kits use the same laboratory NAATs and perform equivalently when instructions are followed; point-of-care NAATs match laboratory sensitivity within a few percentage points.

Normal range for Chlamydia test

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

GroupTypical range (Qualitative: negative (not detected) or positive (detected); some reports add 'equivocal' or 'invalid'. No numeric value)Notes
Negative, collected 2 or more weeks after the last possible exposureNot detectedReliable negative. Repeat only after a new exposure, or at your next routine screen (yearly under 25 or with new partners).
Negative, collected within 1 to 2 weeks of exposureNot detectedNot conclusive; early infection can be below detection. Repeat at 2 weeks, or sooner if symptoms develop.
Positive, first resultDetectedChlamydia infection at the site sampled. Treatment, partner notification, testing for other STIs and a 3-month retest follow. Specificity is above 99 percent, so a positive is almost always real.
Positive within 3 to 4 weeks of completing treatmentDetectedUsually residual DNA from dead organisms rather than treatment failure; NAATs can stay positive for about 3 weeks. Retest after 4 weeks unless symptoms persist or reinfection is likely.
Positive at the 3-month retestDetectedMost often reinfection from an untreated or new partner (about 14 percent of women and 1 in 10 men are reinfected within a year). Treated again, with renewed partner treatment.
Positive in pregnancyDetectedTreated with a pregnancy-safe regimen; a repeat test 4 weeks after treatment confirms clearance and a further test in the third trimester or at 3 months checks for reinfection, because untreated infection can cause neonatal eye infection and pneumonia.
Equivocal or invalidNo usable resultSignal near the cutoff or an inhibited reaction (blood, lubricant, very concentrated urine). Repeat with a fresh sample, preferably a vaginal swab in women.

Positive chlamydia test

A positive result means Chlamydia trachomatis DNA or RNA was detected at the site sampled: the genital tract for urine or a vaginal or cervical swab, the rectum or throat for those swabs. Because specificity is over 99 percent, a positive in someone who has had sex is almost always a true infection, even without symptoms, which is the case for most women and about half of men. Chlamydia is a reportable infection, so the laboratory notifies the health department, which can help with confidential partner notification.

Treatment is straightforward and effective: a 7-day course of doxycycline clears 97 to 99 percent of urogenital infections, and a single dose of azithromycin is used in pregnancy. The reason prompt treatment matters is what untreated infection does over months: in women, roughly 1 in 6 to 1 in 10 untreated infections ascend to cause pelvic inflammatory disease, which in turn causes tubal infertility, ectopic pregnancy and chronic pelvic pain; in men, epididymitis; in either, reactive arthritis and an increased susceptibility to HIV. Partners from the previous 60 days (or the most recent partner if longer ago) need testing and treatment, and in most states your clinician can provide a prescription for your partner without seeing them (expedited partner therapy).

After treatment, abstain from sex for 7 days after a single-dose regimen or until the 7-day course is finished and your partner has also been treated, otherwise you simply pass it back and forth. A repeat test to confirm clearance is not routinely needed except in pregnancy, if symptoms persist, or if you may have missed doses, and it should not be done before 4 weeks because residual DNA gives a false positive. The 3-month retest is for reinfection, which affects 10 to 20 percent of people and is the main driver of complications.

Common causes

  1. Current genital infection acquired through vaginal or anal sex

    The usual reason. Transmission per act is high, with roughly a 1 in 10 to 1 in 3 chance of acquiring chlamydia from a single exposure to an infected partner, and most infections are found by screening rather than symptoms.

  2. Rectal infection

    Common in men who have sex with men and, surprisingly, in women with urogenital chlamydia even without anal sex (found in a third to two-thirds in some studies, probably by spread from vaginal secretions). Doxycycline clears rectal infection in close to 100 percent of cases versus about 74 percent for single-dose azithromycin, which is why doxycycline is now first-line.

  3. Throat (pharyngeal) infection

    Acquired through oral sex, usually without symptoms, and less common and more likely to clear spontaneously than throat gonorrhea. It is only found if a throat swab is taken; a urine test will not detect it.

  4. Reinfection from an untreated or new partner

    The commonest reason for a second positive. Between 10 and 20 percent of people test positive again within a year, most within 3 to 6 months, usually because a partner was not treated or a new partner was infected.

  5. Residual DNA after successful treatment

    NAATs detect dead organisms, so a test within 3 weeks of finishing antibiotics is frequently positive without live infection; RNA-based assays clear a little faster than DNA-based ones.

  6. Lymphogranuloma venereum (LGV)

    Infection with the invasive L1 to L3 strains, seen mainly as rectal pain, bleeding and discharge in men who have sex with men. A standard NAAT reports it simply as chlamydia positive; specialized typing identifies LGV, which needs 21 days of treatment instead of 7.

  7. Treatment failure or missed doses

    Uncommon with doxycycline (under 3 percent for urogenital infection) but higher with single-dose azithromycin, particularly for rectal infection, and with vomiting or missed doses. Persistent symptoms after treatment warrant a retest and a review of adherence.

  8. False positive

    Rare (specificity above 99 percent), but more likely in people with no plausible exposure, where a positive is more often spurious. Laboratory contamination and rare cross-reactions are the usual explanations; a repeat on a fresh sample, ideally with a different assay, settles it.

Symptoms that can go with it

  • None in about 70 percent of women and half of men, which is why screening rather than symptoms finds most infections
  • In women: unusual vaginal discharge, bleeding between periods or after sex, burning on urination, lower abdominal pain or pain during sex
  • In men: clear or cloudy discharge from the penis, burning on urination, itching at the tip, and pain or swelling in one testicle (epididymitis)
  • Rectal infection: pain, discharge, bleeding or a feeling of needing to pass stool; often no symptoms at all
  • Throat infection: usually none, occasionally a mild sore throat
  • Eye infection (conjunctivitis) from contact with infected secretions, with redness, discharge and irritation
  • Weeks later in a minority: painful swollen joints, eye inflammation and urinary symptoms together (reactive arthritis), or fever and pelvic pain from pelvic inflammatory disease

Negative chlamydia test

A negative result means no Chlamydia trachomatis genetic material was detected in the sample you gave. If that sample was the right one for your exposure (a vaginal swab or first-catch urine for vaginal sex, a rectal swab for receptive anal sex, a throat swab for oral sex) and was collected at least 2 weeks after your last possible exposure, you can be confident you do not have chlamydia at that site. NAATs miss only 2 to 8 percent of infections when the sample is correct.

A negative test does not cover other infections with similar symptoms. Persistent discharge, burning or pelvic pain with a negative chlamydia test points toward gonorrhea, trichomoniasis, Mycoplasma genitalium, bacterial vaginosis, a urinary tract infection, herpes or non-infectious causes, each of which has its own test. It also says nothing about future exposures: a yearly test is recommended for sexually active women under 25 and anyone with new partners.

Common causes

  1. No infection

    The expected result in more than 90 percent of people screened; chlamydia prevalence in young sexually active women is around 4 to 5 percent and lower in older adults.

  2. Tested too early

    The organism needs days to multiply to detectable levels after exposure; a test within the first week can miss an infection that would be positive at 2 weeks.

  3. Wrong site sampled

    A urine or vaginal test does not detect rectal or throat infection; a third or more of rectal infections in men who have sex with men have no genital infection and are missed by urine testing alone.

  4. Midstream or recently voided urine

    Chlamydia lives in urethral cells, which are washed out in the first part of the stream. A midstream sample, or urinating within an hour before the test, lowers sensitivity, particularly in women.

  5. Recent antibiotics

    Doxycycline taken for acne, azithromycin for a chest infection or other antibiotics in the previous few weeks can clear or suppress chlamydia, producing a negative test in someone who was infected; partners may still carry it.

Symptoms that can go with it

  • None; a negative result is the expected finding
  • Symptoms that continue despite a negative test need a different explanation and usually tests for gonorrhea, trichomoniasis, Mycoplasma genitalium or a urinary infection

Read it alongside

  • Gonorrhea NAAT — run on the same sample; co-infection occurs in 10 to 40 percent of people with gonorrhea, and treatment covers both when either is positive and the other is unknown.
  • Trichomonas vaginalis NAAT — the most common non-viral STI, often with similar discharge; standard CT/NG tests do not include it unless requested.
  • Mycoplasma genitalium NAAT — considered when urethritis or cervicitis persists after a negative chlamydia test or after treatment.
  • HIV antigen/antibody test — recommended for everyone diagnosed with chlamydia; untreated STIs raise the risk of acquiring HIV.
  • Syphilis screen (RPR or treponemal antibody) — part of the standard STI panel, and essential if there is a painless genital ulcer or rash.
  • Hepatitis B surface antigen and hepatitis C antibody — baseline for people with new STI diagnoses, with hepatitis B vaccination offered to the non-immune.
  • Urinalysis and urine culture — leukocytes in urine with a negative culture (sterile pyuria) is a classic clue to chlamydia or gonorrhea rather than a bladder infection.
  • Pregnancy test (hCG) — changes the antibiotic chosen and adds a repeat test 4 weeks after treatment.

What usually happens next

  1. A positive result is treated the same day it is received; the CDC's first-line regimen is doxycycline for 7 days, with azithromycin in pregnancy or where doxycycline cannot be used. Tell your clinician if you could be pregnant or have had a reaction to tetracyclines.
  2. Every partner from the previous 60 days is told, tested and treated, whether or not their test is positive; ask about expedited partner therapy if a partner cannot attend. Abstain from sex until 7 days after both of you have completed treatment.
  3. Ask for the rest of the STI panel if it was not done: gonorrhea (usually already included), HIV, syphilis and, depending on exposure, throat and rectal swabs, trichomoniasis and hepatitis B and C.
  4. A repeat test in pregnancy, 4 weeks after treatment, confirms clearance; outside pregnancy, retest only if symptoms persist or doses were missed, and not before 4 weeks.
  5. Everyone retests at 3 months, regardless of partner treatment, because reinfection affects 10 to 20 percent. Put the date in your calendar when you get the result.
  6. A negative test with ongoing symptoms is followed by tests for gonorrhea, trichomoniasis, Mycoplasma genitalium, urinary infection and herpes as appropriate, rather than repeating the chlamydia test.

Diet, lifestyle and natural levers with evidence

What can move Chlamydia test once the cause is known. Nothing here replaces finding the cause.

Collect the right sample at the right time

Strong evidence

Nothing dietary changes a chlamydia result; sample quality and timing do. Testing 2 weeks after exposure avoids the early false negative, a self-collected vaginal swab detects 96 to 98 percent of infections versus 85 to 93 percent for female urine in head-to-head studies, first-catch rather than midstream urine matters in men and women, and rectal or throat swabs are needed if those sites were exposed. Urine should be the first 20 to 30 mL after not urinating for at least an hour.

Make sure partners are treated before you have sex again

Strong evidence

In a randomized trial of 2,751 people with chlamydia or gonorrhea, giving patients medication or prescriptions to deliver to their partners reduced persistent or recurrent infection from 13 percent to 10 percent, and a meta-analysis of partner-therapy trials found about a 27 percent reduction in reinfection. Ping-pong reinfection from an untreated partner is the main reason people test positive again.

Retest at 3 months even if you feel fine

Strong evidence

A systematic review of repeat-infection studies found a median reinfection rate of about 14 percent in women within a year of treatment, with the peak in the first 3 to 6 months, and similar or slightly lower rates in men. Repeat infection carries a higher cumulative risk of pelvic inflammatory disease than a first infection, so the 3-month retest is one of the most effective steps in preventing complications.

Consistent condom use

Moderate evidence

Observational studies that correctly account for whether a partner was infected find consistent condom use reduces chlamydia and gonorrhea acquisition by roughly 60 percent or more, with weaker protection when use is inconsistent or condoms are applied late. Chlamydia is transmitted by secretions rather than skin contact, so, unlike HPV or herpes, a condom covers the route of transmission.

Antibiotics, not supplements, clear the infection

Strong evidence

No herb, probiotic, cranberry, garlic or vitamin product has ever been shown to clear Chlamydia trachomatis, and leaving it untreated in the hope it resolves is a poor bet: about half of untreated infections in women persist beyond a year, and the risk of pelvic inflammatory disease accumulates over that time. Doxycycline clears 97 to 99 percent of urogenital infections and virtually all rectal infections in trials; azithromycin clears a few percent fewer.

Calcium, iron, magnesium and zinc supplements, antacids and dairy bind doxycycline and cut its absorption; take them at least 2 to 3 hours apart. Doxycycline causes sun sensitivity and is avoided in pregnancy, where azithromycin is used.

When to see a clinician promptly

  • Lower abdominal or pelvic pain with fever, pain during sex, or abnormal bleeding alongside a positive test or a known exposure: possible pelvic inflammatory disease, which needs treatment the same day to protect fertility.
  • Sudden severe pain or swelling in a testicle: epididymitis from chlamydia is treated urgently, and testicular torsion, which can look similar, is a surgical emergency within hours.
  • A positive test in pregnancy, or a positive test in a partner of someone who is pregnant: treatment and a repeat test protect the baby from eye infection and pneumonia at birth.
  • Symptoms that persist more than a week after finishing treatment, or that return: retesting, a check for reinfection or Mycoplasma genitalium, and sometimes a different antibiotic.
  • A newborn with sticky, red eyes in the first 2 weeks or a staccato cough and breathlessness at 1 to 3 months whose mother was not tested in pregnancy.
  • After sexual assault: emergency care offers preventive treatment for chlamydia and gonorrhea, emergency contraception and HIV PEP, all of which are time-sensitive.

Frequently asked questions

How long does a chlamydia test take?

Giving the sample takes a minute or two: a self-collected vaginal swab, a first-catch urine sample, or a throat or rectal swab. Laboratory results usually come back in 1 to 3 business days, point-of-care NAATs in some clinics give a result in 30 to 90 minutes while you wait, and mailed home-collection kits take about 2 to 5 days after the lab receives them.

How soon after exposure can you test for chlamydia?

A NAAT can detect chlamydia within a few days of exposure, but the organism needs time to multiply, so a test in the first week can miss an early infection. Most clinics advise testing at 2 weeks for a conclusive result; if you test earlier because of symptoms or anxiety and the result is negative, repeat it at 2 weeks. Symptoms, when they occur, usually start 1 to 3 weeks after exposure.

How accurate is a chlamydia urine test?

Very accurate in men: first-catch urine detects 95 to 98 percent of urethral infections, as well as a swab does. In women it is somewhat less sensitive, around 85 to 93 percent, because the infection sits in the cervix and vagina rather than the urethra, which is why a self-collected vaginal swab (96 to 98 percent) is preferred. Specificity is over 99 percent for both. Urine must be first-catch rather than midstream, and it does not detect throat or rectal infection.

Can a chlamydia test be a false positive?

Rarely. NAATs have a specificity above 99 percent, so fewer than 1 in 100 uninfected people get a positive result, and in sexually active people a positive is almost always real. False positives are relatively more likely when there has been no plausible exposure, and within 3 to 4 weeks of treatment, when DNA from dead bacteria is still detectable. If a result does not fit, a repeat on a fresh sample, ideally with a different assay, resolves it.

Why is my chlamydia test still positive after treatment?

The commonest reason is testing too soon: NAATs detect DNA from dead organisms, which can persist for about 3 weeks after antibiotics, so a test in that window is often positive without live infection. The next commonest is reinfection from a partner who was not treated or a new partner. True treatment failure is uncommon (under 3 percent with doxycycline) but more likely with single-dose azithromycin for rectal infection or with missed doses. Retest after 4 weeks and make sure partners were treated.

Do I need to be retested after chlamydia treatment?

Two different retests exist. A test to confirm the infection has cleared is only routinely recommended in pregnancy (4 weeks after treatment), when symptoms persist, or when doses were missed. A retest at 3 months is recommended for everyone, because 10 to 20 percent of people are reinfected within a year, most within 3 to 6 months, and repeat infection carries a higher risk of pelvic inflammatory disease.

Can you get chlamydia in your throat, and will a urine test find it?

Yes, chlamydia can infect the throat through oral sex, though it is less common there than gonorrhea and usually causes no symptoms. A urine or vaginal test only samples the genital tract, so throat and rectal infections are missed unless a swab is taken from each exposed site. Ask for throat and rectal swabs if those sites were exposed; most assays are FDA-cleared for them and self-collection is acceptable.

How long after a positive chlamydia test can I have sex again?

Wait until 7 days after a single-dose treatment, or until you have finished the full 7-day doxycycline course, and until your partner has also completed treatment, whichever is later. Having sex sooner risks passing the infection straight back. Condoms reduce but do not fully remove that risk during the treatment week, and everyone should retest at 3 months.

References

  1. Chlamydia test. MedlinePlus, US National Library of Medicine (2024)View source
  2. Workowski KA, Bachmann LH, Chan PA, et al.. Sexually transmitted infections treatment guidelines, 2021. MMWR Recommendations and Reports (2021)
  3. Papp JR, Schachter J, Gaydos CA, Van Der Pol B. Recommendations for the laboratory-based detection of Chlamydia trachomatis and Neisseria gonorrhoeae — 2014. MMWR Recommendations and Reports (2014)
  4. US Preventive Services Task Force. Screening for chlamydia and gonorrhea: US Preventive Services Task Force recommendation statement. JAMA (2021)
  5. Lunny C, Taylor D, Hoang L, et al.. Self-collected versus clinician-collected sampling for chlamydia and gonorrhea screening: a systematic review and meta-analysis. PLoS ONE (2015)
  6. Golden MR, Whittington WL, Handsfield HH, et al.. Effect of expedited treatment of sex partners on recurrent or persistent gonorrhea or chlamydial infection. New England Journal of Medicine (2005)
  7. Hosenfeld CB, Workowski KA, Berman S, et al.. Repeat infection with chlamydia and gonorrhea among females: a systematic review of the literature. Sexually Transmitted Diseases (2009)
  8. Dombrowski JC, Wierzbicki MR, Newman LM, et al.. Doxycycline versus azithromycin for the treatment of rectal chlamydia in men who have sex with men: a randomized controlled trial. Clinical Infectious Diseases (2021)
  9. Geisler WM, Lensing SY, Press CG, Hook EW. Spontaneous resolution of genital Chlamydia trachomatis infection in women and protection from reinfection. Journal of Infectious Diseases (2013)
  10. Renault CA, Israelski DM, Levy V, Fujikawa A, Kellogg TA, Klausner JD. Time to clearance of Chlamydia trachomatis ribosomal RNA in women treated for chlamydial infection. Sexual Health (2011)
  11. Chlamydia trachomatis. Mayo Clinic (2023)
  12. Chlamydial, mycoplasmal, and ureaplasmal mucosal infections. Merck Manual Professional Version (2024)

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