Key Takeaways
- The CDC 2021 STI Treatment Guidelines moved doxycycline 100 mg BID × 7 days to the preferred regimen; azithromycin 1 g single dose is now an alternative.
- NAAT testing is the gold standard — sensitivity above 90%, specificity above 99%, and valid for urogenital, rectal, and pharyngeal specimens.
- All sexually active women under 25 should be screened annually; pregnant women need test of cure at 4 weeks post-treatment.
- Expedited partner therapy (EPT) is permissible in 48 states and the District of Columbia as of 2024; always verify your state's law.
- Reinfection within 3 months occurs in 10–20% of treated patients — primarily because partners go untreated.
- Untreated chlamydia raises the risk of pelvic inflammatory disease by 136%, ectopic pregnancy by 87%, and infertility by 85% compared to infection-negative women.
Chlamydia is the most commonly reported bacterial infection in the United States, with approximately 1.6 million cases diagnosed annually — and that number almost certainly undercounts the true burden, since most infections produce no symptoms.[1] What makes this infection clinically important is not how it presents, but what it causes when it goes undetected and untreated. The downstream consequences — pelvic inflammatory disease, ectopic pregnancy, tubal infertility, epididymitis — are largely preventable with timely diagnosis and correct treatment.
Treatment recommendations changed meaningfully in 2021. The CDC's updated STI Treatment Guidelines demoted azithromycin from its preferred position and placed doxycycline at the top of the regimen list. Many clinicians and patients still aren't aware of that shift. This guide explains exactly why that change was made, who it applies to, and what else you need to know about managing chlamydia correctly — from initial testing to partner treatment.
Why the CDC Changed Its Chlamydia Treatment Recommendation
For roughly two decades, azithromycin 1 g as a single oral dose was the standard first-line treatment for chlamydia. It was convenient, directly observed in clinical settings, and had equivalent efficacy to doxycycline for urogenital infection in controlled trials. In 2021, the CDC moved it to second-line status.[1]
The evidence driving that decision came primarily from studies of rectal chlamydia. A landmark randomized controlled trial published in Clinical Infectious Diseases compared doxycycline versus azithromycin specifically for rectal C. trachomatis infection in men who have sex with men. Microbiologic cure was 100% with doxycycline versus 74% with azithromycin — a 26-percentage-point difference that was highly statistically significant.[3]
What makes this particularly significant for women: studies indicate that C. trachomatis is detectable at the anorectal site in 33–83% of women who have urogenital infection — and this rectal co-infection does not correlate with reported anal sexual activity.[1] In other words, a woman treated with azithromycin for a positive vaginal NAAT may have a concurrent rectal infection that azithromycin fails to cure. That untreated rectal reservoir can then re-seed the genital tract, producing apparent treatment failure or reinfection. Doxycycline clears infection at all three sites — urogenital, rectal, and oropharyngeal — making it the clinically sound choice for all patients.
The change was not driven by antibiotic resistance concerns (unlike the evolution of gonorrhea treatment). C. trachomatis does not develop classic acquired resistance to azithromycin. The issue is pharmacokinetics and tissue penetration at the rectal mucosa, not resistance.
Current Treatment Regimens
Standard Regimens for Adolescents and Adults (Non-Pregnant)
| Regimen | Dose | Classification | Notes |
|---|---|---|---|
| Doxycycline | 100 mg orally twice daily × 7 days | Preferred (first-line) | Superior efficacy for rectal and oropharyngeal sites. Take with food to reduce GI upset. Avoid in pregnancy (2nd/3rd trimester). |
| Azithromycin | 1 g orally in a single dose | Alternative | Retained when adherence to a 7-day course is a substantial concern. Clinically appropriate for urogenital infection in women. Less effective for rectal chlamydia. |
| Levofloxacin | 500 mg orally once daily × 7 days | Alternative | Effective but more expensive. Reserve when other options are contraindicated. |
One practical note on doxycycline: a delayed-release 200 mg formulation taken once daily for 7 days is equally effective as the twice-daily standard formulation and produces fewer gastrointestinal side effects.[1] The cost is higher, but for patients prone to GI intolerance, it is a reasonable option.
Treatment During Pregnancy
Doxycycline and levofloxacin are contraindicated after the first trimester. Azithromycin 1 g as a single oral dose is the preferred treatment for pregnant patients.[1] Amoxicillin 500 mg three times daily for 7 days is listed as an alternative. Erythromycin is no longer recommended because its gastrointestinal side effects frequently lead to nonadherence, and systematic reviews have raised concerns about macrolide use in pregnancy and adverse neonatal outcomes.
What I tell pregnant patients with chlamydia: treatment is not optional. Untreated maternal chlamydia increases the risk of preterm delivery and can be transmitted to the neonate during birth, causing ophthalmia neonatorum or pneumonia.
Pharyngeal and Rectal Chlamydia
Pharyngeal chlamydia is not commonly screened for in routine practice, but it does occur — most often in individuals who engage in receptive oral sex. Clinical significance is still being studied, though C. trachomatis has been detected at this site and doxycycline appears more efficacious than azithromycin based on observational data.[1]
Rectal chlamydia is clinically important and often asymptomatic. The CDC recommends annual rectal screening for men who have sex with men, and notes that rectal testing should be considered for women based on reported sexual behaviors and individual risk — discussed openly between patient and provider. Self-collected rectal swabs are acceptable for NAAT testing, lowering the barrier to screening at extragenital sites.
NAAT Testing: The Gold Standard for Diagnosis
Nucleic acid amplification testing (NAAT) is the only diagnostic method you should accept for chlamydia. It detects C. trachomatis DNA or RNA with sensitivity typically above 90% and specificity above 99% across multiple studies.[7] Point-of-care antigen tests and older non-amplified probes exist but are substantially less sensitive and have no place in current clinical practice for this indication.
Specimen Collection
- Women: Vaginal swabs are the preferred specimen type — higher sensitivity than endocervical swabs or urine. Patients can self-collect vaginal swabs with equivalent accuracy to clinician-collected specimens.
- Men: First-catch urine (the initial stream of urination, which carries the highest bacterial load from the urethra) is preferred.
- Extragenital sites: Rectal and pharyngeal swabs can be tested with FDA-cleared NAATs. Most modern NAAT platforms test for both C. trachomatis and N. gonorrhoeae from a single specimen.
Non-viable organism DNA can persist in tissue for weeks after successful treatment. Running a NAAT within 4 weeks of completing therapy can yield a false-positive result, leading to unnecessary re-treatment and patient anxiety. Test of cure (repeat NAAT) in non-pregnant adults is not routinely recommended at all — unless symptoms persist, adherence was uncertain, or reinfection is suspected.[1]
Screening Recommendations
The USPSTF gives a Grade B recommendation for annual chlamydia screening in all sexually active women 24 years and younger, and in women 25 and older who have at least one elevated-risk factor: a new partner, multiple concurrent partners, inconsistent condom use, or a prior STI history.[6]
| Population | Recommended Screening |
|---|---|
| Sexually active women under 25 | Annually (USPSTF Grade B) |
| Women 25+ with elevated risk factors | Annually (USPSTF Grade B) |
| All pregnant women under 25 | At first prenatal visit; rescreen third trimester if at risk |
| Pregnant women 25+ with risk factors | At first prenatal visit; rescreen third trimester |
| Men who have sex with men (MSM) | Annually at urethral and rectal sites; every 3–6 months if at elevated risk (on PrEP, HIV-positive, or multiple partners) |
| All patients diagnosed with chlamydia | Retest approximately 3 months after treatment to detect reinfection |
After a positive chlamydia diagnosis, the CDC also recommends co-testing for gonorrhea, HIV, and syphilis at the same visit.[1] MSM who test HIV-negative with a rectal chlamydia diagnosis should be offered HIV pre-exposure prophylaxis (PrEP) if not already on it.
Follow-Up and Special Considerations in Pregnancy
For non-pregnant adults treated with a recommended or alternative regimen, routine test of cure is not advised. The main follow-up action is retesting at approximately 3 months after treatment, not to assess treatment success, but to catch reinfection from a new or previously untreated partner.[1]
Pregnant patients require a different approach. Test of cure — a repeat NAAT — should be performed at approximately 4 weeks after completing therapy, because consequences of persistent infection during pregnancy include preterm delivery and neonatal transmission. Pregnant women also need to be retested 3 months after treatment and again in the third trimester if they are under 25 or have ongoing elevated risk.
Patients should abstain from sexual intercourse for 7 days after completing a 7-day regimen (or 7 days after a single-dose azithromycin) and until all partners have been treated. Resuming sex before partners are treated is the most common driver of reinfection — not treatment failure.
Expedited Partner Therapy: What It Is and Who Can Receive It
Expedited partner therapy (EPT) is the clinical practice of treating the sexual partners of a diagnosed patient by providing them with a prescription or medication directly through the index patient — without the partner being evaluated by a clinician first.[4] The rationale is simple: if partners are not treated, reinfection rates stay high and transmission continues.
The CDC recommends EPT for all patients diagnosed with chlamydia, specifically noting its value for male partners of women with chlamydia or gonorrhea — a population that historically has low rates of follow-through on independent care appointments. EPT should be offered alongside, not instead of, standard partner referral for clinical evaluation when feasible.
As of July 2024, EPT is permissible in 48 states and the District of Columbia.[5] Kansas and South Dakota currently do not allow EPT under existing state law — not because it is explicitly banned, but because current statutes do not provide a legal pathway for it. Oklahoma passed legislation in 2024 making EPT permissible, effective November 2024. State laws vary on which STIs are covered: at least 25 states allow EPT for chlamydia and gonorrhea; Massachusetts allows EPT for chlamydia only; and several states extend coverage to trichomoniasis as well. Always verify your state's current law before issuing an EPT prescription.
EPT Medication for Chlamydia
The preferred EPT regimen for chlamydia partners follows the same CDC 2021 guidelines: doxycycline 100 mg orally twice daily for 7 days, or azithromycin 1 g orally in a single dose. Azithromycin is specifically preferred for EPT when the partner's pregnancy status is unknown, since doxycycline is contraindicated in pregnancy.[4] Levofloxacin 500 mg once daily for 7 days is a listed alternative.
Partners who receive EPT should be instructed to abstain from sex for 7 days after completing treatment and to seek their own clinical evaluation for full STI screening — EPT covers the immediate treatment need, but does not replace a full clinical evaluation.
Reinfection: A Persistent Clinical Problem
Chlamydia reinfection rates are clinically significant and consistently underestimated. Studies report that 10–20% of patients are reinfected within 3 months of completing treatment, and the true rate is higher because most patients are not retested at that interval.[9] Among adolescent women, the cumulative risk of reinfection within one year approaches 11–17%, and within two years, approaches 17–20%.
The dominant driver is not treatment failure — it is untreated partners. Patients return to sexual activity with the same partner who either refused treatment or was never told about the diagnosis. This is why partner notification and EPT are inseparable from chlamydia management.
Repeat infections are not merely inconvenient. Each additional episode of chlamydia incrementally increases the risk of upper reproductive tract damage. Women with two or more positive tests have substantially higher risk of pelvic inflammatory disease than those with a single infection. The CDC recommendation to retest at 3 months exists specifically to catch these new infections early — before silent progression occurs.
I tell patients: the 3-month retest is not checking whether the antibiotics worked. It's checking whether you got reinfected. The antibiotics almost certainly worked if you took them correctly. The retest is about your partners and your behavior after treatment — not the drug. Setting that expectation upfront changes how patients interpret the recommendation.
Complications of Untreated Chlamydia
Most of the harm from chlamydia is not from the acute infection — it is from the chronic, asymptomatic progression that occurs when treatment is delayed or never happens. Understanding these consequences helps patients grasp why screening and treatment matter even when they feel fine.
Pelvic Inflammatory Disease (PID)
PID occurs when chlamydia (or gonorrhea, or both) ascends from the cervix to the uterus, fallopian tubes, and ovaries. Clinical studies estimate that up to 40% of untreated cervical chlamydial infections progress to PID.[8] In a large population-based cohort, women who tested positive for chlamydia had a 2.36-times higher adjusted risk of PID than infection-negative women. PID can present as acute pelvic pain and fever, or it can be entirely subclinical ("silent PID"), discovered only when a patient presents with infertility.
Ectopic Pregnancy
Women with a history of chlamydia diagnosis carry approximately 87% higher risk of ectopic pregnancy compared to uninfected women, based on a large retrospective cohort study.[8] Ectopic pregnancy — implantation of a fertilized egg outside the uterus, most commonly in a fallopian tube — is a surgical emergency and a direct consequence of the tubal scarring that chlamydia-related PID causes. This risk increases with repeat infections.
Tubal Factor Infertility
Salpingitis — inflammation of the fallopian tubes — caused by ascending chlamydial infection can produce fibrosis and blockage that prevents conception. Women with chlamydia have approximately 85% higher adjusted risk of infertility than women who test negative.[8] Screening programs exist precisely because identifying and treating chlamydia before upper tract involvement interrupts this progression.
Epididymitis in Men
In men, untreated urethral chlamydia can ascend through the vas deferens and infect the epididymis — the coiled tube behind the testicle responsible for sperm maturation. Acute epididymitis presents as unilateral scrotal pain, swelling, and tenderness, often with fever. The CDC recommended regimen for sexually transmitted epididymitis is ceftriaxone 500 mg IM in a single dose plus doxycycline 100 mg orally twice daily for 10 days, covering both chlamydia and gonorrhea.[2] Chronic or recurrent epididymitis can affect sperm quality and fertility.
Lymphogranuloma Venereum (LGV)
LGV is caused by specific serovars (L1–L3) of C. trachomatis and represents a more invasive form of chlamydial infection. It is uncommon in the general U.S. population but occurs in clusters among MSM, where it can produce severe proctocolitis. LGV requires longer treatment: doxycycline 100 mg twice daily for 21 days, rather than the standard 7-day course.[2] If rectal chlamydia does not respond to standard doxycycline treatment or presents with severe proctitis, LGV serovars should be considered.
Telehealth and Chlamydia Management
Chlamydia is among the STIs most amenable to telehealth care. The full diagnostic and treatment pathway — history, test ordering, antibiotic prescribing, EPT, partner notification counseling, and retest scheduling — can be completed without an in-person visit in most cases.
Unlike gonorrhea, which requires ceftriaxone administered by injection, chlamydia treatment is entirely oral. A physician or advanced practice provider can review your sexual history via a secure video visit, order a NAAT at a local laboratory or through a home collection kit, and send the prescription electronically to your pharmacy. EPT prescriptions for partners can also be issued during the same visit in states where EPT is permissible.
The main limitation of telehealth for STI care is that it cannot replace in-person examination when a clinical finding needs direct assessment — suspected PID with abdominal tenderness, epididymitis, or LGV proctitis, for example. For those presentations, an in-person visit or emergency evaluation is appropriate.
From a public health standpoint, telehealth lowers barriers that have historically kept chlamydia rates elevated: geographic distance from clinics, stigma, time constraints, and privacy concerns. Patients who might delay or avoid an in-person visit for STI testing can access evaluation and treatment the same day via a video visit, which has meaningful downstream effects on transmission and complication rates.
When to Seek Prompt or Emergency Care
- Acute pelvic pain with fever — possible PID, which can progress to tubo-ovarian abscess requiring hospitalization or surgery
- Unilateral scrotal pain and swelling — evaluate for epididymitis; also requires imaging to rule out testicular torsion, which is a surgical emergency
- Severe rectal pain, bleeding, or discharge with fever — possible LGV proctocolitis or rectal gonorrhea requiring further workup
- Symptoms during pregnancy — any suspected STI in pregnancy requires same-day evaluation and treatment
- Persistent symptoms after completing treatment — could indicate treatment failure, reinfection, or a concurrent infection that was not initially tested for
- Eye redness with discharge in a newborn — possible chlamydial ophthalmia neonatorum; requires immediate evaluation
Most uncomplicated chlamydial infections do not produce urgent symptoms — that is precisely what makes them dangerous. The dangerous presentations above indicate that the infection has already progressed beyond the lower genital or urinary tract. Do not wait to seek care for these findings.
Frequently Asked Questions
The CDC 2021 STI Treatment Guidelines designate doxycycline 100 mg orally twice daily for 7 days as the preferred first-line treatment for chlamydia in non-pregnant adolescents and adults.[1] Azithromycin 1 g as a single oral dose is now listed as an alternative, not the primary recommendation. The switch was driven by clinical evidence showing doxycycline is significantly more effective for rectal chlamydial infections, which can occur concurrently in up to 33–83% of women with urogenital infection regardless of reported sexual behavior.
Yes. Chlamydia is one of the STIs most amenable to telehealth management. A clinician can review your sexual history, order NAAT testing at a local lab or via a home collection kit, and prescribe doxycycline or azithromycin electronically. Unlike gonorrhea, which requires an injectable antibiotic, chlamydia treatment is oral and can be dispensed at any pharmacy. Telehealth visits also allow clinicians to issue expedited partner therapy prescriptions in states where it is legally permitted.
For non-pregnant adults treated with doxycycline or azithromycin, routine test of cure is not recommended unless symptoms persist, adherence was questionable, or reinfection is suspected.[1] The CDC specifically advises against NAAT testing within 4 weeks of completing treatment because residual non-viable organisms can produce false-positive results. For pregnant patients, test of cure by NAAT at approximately 4 weeks post-treatment is required, along with retesting at 3 months and in the third trimester if ongoing risk exists.
Expedited partner therapy (EPT) is the practice of providing a prescription or medication directly to a patient to take to their sexual partners, without those partners being examined by a clinician first.[4] The CDC recommends EPT for all patients diagnosed with chlamydia as a way to reduce reinfection and interrupt transmission chains. As of 2024, EPT is permissible in 48 states and the District of Columbia. Kansas and South Dakota currently do not allow the practice under existing state law.
Reinfection rates are clinically significant. Studies report that 10–20% of patients are reinfected within 3 months of treatment, most commonly because partners were not treated concurrently.[9] The CDC recommends retesting approximately 3 months after treatment for all patients — not because treatment failed, but because new exposure is common. Among adolescent women, reinfection rates within one year can reach 11–17%. Repeat infections increase the risk of pelvic inflammatory disease substantially.
Yes. Untreated chlamydia in women can ascend to the upper reproductive tract and cause pelvic inflammatory disease (PID). Women with a confirmed chlamydia diagnosis have approximately 2.4 times the risk of PID, 1.9 times the risk of ectopic pregnancy, and 1.9 times the risk of infertility compared to women who test negative.[8] In men, untreated chlamydia can cause epididymitis, which presents as scrotal pain and swelling and can affect fertility if untreated. Prompt treatment and partner notification are the most effective tools for preventing these outcomes.
The USPSTF and CDC recommend annual chlamydia screening for all sexually active women 24 years and younger, and for women 25 and older who have elevated risk factors (new or multiple partners, inconsistent condom use, or prior STI).[6] All pregnant women under 25 should be screened at their first prenatal visit. Men who have sex with men should be screened at sites of contact — urethral and rectal — at least annually, and every 3 to 6 months if at elevated risk. Evidence is insufficient to recommend routine screening of heterosexual men at low risk, though screening is reasonable in high-prevalence settings.
Azithromycin remains effective for urogenital chlamydia in women. It lost its preferred status because of substantially lower efficacy for rectal chlamydial infection. A randomized controlled trial published in Clinical Infectious Diseases (2021) found microbiologic cure rates of 100% with doxycycline versus 74% with azithromycin for rectal chlamydia.[3] Because rectal chlamydia co-occurs with urogenital infection in a large proportion of women — even without reported anal sex — the CDC concluded that doxycycline should be standard for all adults. It is not a resistance issue; it is about tissue penetration at the rectal mucosa.
Nucleic acid amplification testing (NAAT) detects C. trachomatis DNA or RNA with sensitivity typically above 90% and specificity above 99%.[7] It outperforms older diagnostic methods — antigen detection tests, cell culture, and non-amplified probes — across all specimen types. NAAT can be run on vaginal swabs (preferred for women), first-catch urine (preferred for men), rectal swabs, and pharyngeal swabs using a single platform. A positive NAAT result is sufficient to treat — culture confirmation is not required in clinical practice.
Yes. The CDC recommends that any person diagnosed with chlamydia be tested for gonorrhea, HIV, and syphilis at the same visit.[1] Chlamydia and gonorrhea co-infection is common, and gonorrhea requires different treatment — ceftriaxone given by injection — that cannot be substituted with oral antibiotics alone. Most modern NAAT platforms test for both organisms simultaneously using a single specimen, so no additional sample collection is required. MSM who receive a rectal chlamydia diagnosis and are HIV-negative should also be offered PrEP.
References
- Centers for Disease Control and Prevention. Chlamydial Infections — STI Treatment Guidelines, 2021. Published July 22, 2021. https://www.cdc.gov/std/treatment-guidelines/chlamydia.htm
- Centers for Disease Control and Prevention. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(RR-4):1–187. https://www.cdc.gov/mmwr/volumes/70/rr/rr7004a1.htm
- Khosropour CM, Dombrowski JC, Barbee LA, et al. Doxycycline Versus Azithromycin for the Treatment of Rectal Chlamydia in Men Who Have Sex With Men: A Randomized Controlled Trial. Clin Infect Dis. 2021;73(5):824–831. https://pubmed.ncbi.nlm.nih.gov/33606009/
- Centers for Disease Control and Prevention. Expedited Partner Therapy — Clinical Guidance. Updated July 16, 2024. https://www.cdc.gov/sti/hcp/clinical-guidance/expedited-partner-therapy.html
- Centers for Disease Control and Prevention. Legal Status of Expedited Partner Therapy (EPT) by State. Updated July 2, 2024. https://www.cdc.gov/sti/php/ept-legal-status/index.html
- U.S. Preventive Services Task Force. Chlamydia and Gonorrhea: Screening. Published September 14, 2021. https://www.uspreventiveservicestaskforce.org/uspstf/recommendation/chlamydia-and-gonorrhea-screening
- Centers for Disease Control and Prevention. Recommendations for the Laboratory-Based Detection of Chlamydia trachomatis and Neisseria gonorrhoeae — 2014. MMWR Recomm Rep. 2014;63(RR-02):1–19. https://pmc.ncbi.nlm.nih.gov/articles/PMC4047970/
- van Oeffelen L, Heijne JCM, Heijman T, et al. Chlamydia trachomatis and the Risk of Pelvic Inflammatory Disease, Ectopic Pregnancy, and Female Infertility. Clin Infect Dis. 2019;69(9):1517–1525. https://pmc.ncbi.nlm.nih.gov/articles/PMC6792126/
- Kerani RP, Stenger M, Armbruster B, et al. High Rates of Repeat Chlamydial Infections among Young Women. Sex Transm Dis. 2013;40(1). https://pmc.ncbi.nlm.nih.gov/articles/PMC6291349/
- Centers for Disease Control and Prevention. STI Screening Recommendations. Updated March 13, 2025. https://www.cdc.gov/std/treatment-guidelines/screening-recommendations.htm