PassFinals
Sexual Health

Chlamydia

Chlamydia trachomatis is an often-silent sexually transmitted infection of columnar epithelium. The high-yield priorities are site-appropriate NAAT, prompt treatment, partner notification, pregnancy-aware prescribing and recognition of ascending or extragenital complications.

In a nutshell

Chlamydia is an often-asymptomatic STI detected by site-appropriate NAAT. Treat uncomplicated infection promptly with doxycycline, notify and treat partners, avoid sex until the treatment and partner pathway is complete, arrange selective test of cure and offer retesting for reinfection. Fever, pelvic or testicular pain, severe proctitis, pregnancy or significant eye symptoms changes the pathway.

Classic presentation

An asymptomatic young woman or other person with a womb or ovaries found through screening or partner notification, or cervicitis with post-coital bleeding, or urethritis with discharge and dysuria.

Key points

  • Most chlamydia is asymptomatic. In England, the NCSP’s proactive community screening focus is young women and other young people with a womb or ovaries; sexual health services continue to test anyone with symptoms, exposure or another indication.
  • NAAT is the standard test. Use a vulvovaginal swab or appropriate genital sample, first-catch urine in men, and add rectal or pharyngeal samples when exposure or symptoms make those sites relevant.
  • For uncomplicated urogenital, pharyngeal or rectal infection, doxycycline 100 mg twice daily for 7 days is first line. See BNF and current BASHH guidance for prescribing and contraindications.
  • Do not use old single-dose azithromycin teaching as the routine first-line answer: BASHH moved away from it because of rectal treatment failure and Mycoplasma genitalium macrolide-resistance concerns.
  • Pregnancy needs current BASHH and BNF review. A short doxycycline course may be considered only in selected early pregnancy when the full course ends before 15 weeks; use pregnancy-appropriate alternatives later and arrange test of cure.
  • Partner notification and treatment are essential. Without this, reinfection is common and a negative follow-up test can be misleading.
  • Routine test of cure is not needed after uncomplicated genital infection, but use it in pregnancy, persistent symptoms, suspected poor adherence and diagnosed rectal infection according to current guidance. Offer retesting around 3 months for reinfection.
  • Treat suspected PID empirically without waiting for swab results. Sudden severe testicular pain is testicular torsion until proven otherwise, not simply epididymo-orchitis.
  • Severe proctitis or bloody rectal discharge raises LGV and needs specialist sexual-health assessment rather than repeated uncomplicated-chlamydia courses.

First-line investigation

Site-directed NAAT, with a full sexual health screen and pregnancy test when relevant.

Management

Recognise complications and pregnancy

  • Check for PID, epididymo-orchitis, testicular torsion, severe proctitis, eye disease, pregnancy and safeguarding concerns before treating a positive result as uncomplicated infection.5,6,8,2

Sample every relevant site

  • Take site-directed NAAT and offer a full sexual health screen. Use a pregnancy test or pregnancy-specific history when relevant, and do not let a negative genital sample falsely reassure after extragenital exposure.1,7,2

Treat and prevent transmission

  • Use doxycycline 100 mg twice daily for 7 days for uncomplicated infection. See BNF and current BASHH guidance for pregnancy, breastfeeding, interactions, adherence and alternatives; notify and treat relevant partners.1,7,9,10,3

Treat the complication, not just the swab

  • Start empirical broad-spectrum treatment for suspected PID, urgently exclude torsion in severe testicular pain and refer severe proctitis, eye disease, neonatal infection or suspected LGV.5,6,1

Confirm the pathway is complete

  • Advise abstinence until the patient and relevant partners have completed treatment, arrange selective test of cure and offer retesting around 3 months to detect reinfection. Give return advice for fever, pelvic pain, testicular pain, eye symptoms or persistent discharge.11,1,2

Exam traps

  • A negative genital sample does not exclude rectal or pharyngeal infection when those sites were not tested.
  • Doxycycline is now the routine first-line treatment for uncomplicated infection; single-dose azithromycin is not the default BASHH answer.
  • Do not label every pregnant patient as unable to receive doxycycline without checking current BASHH and BNF guidance; timing and specialist judgement matter.
  • Do not delay empirical PID treatment while waiting for NAAT results.
  • Partner notification is part of treatment, not an optional public-health add-on.
  • Do not call a test performed too soon after treatment a test of cure: residual DNA can produce a positive NAAT.
  • Sudden severe unilateral scrotal pain requires urgent torsion assessment.

Illustrations

Chlamydial developmental cycleDiagram of the elementary body attaching to and entering columnar epithelium, converting to a reticulate body, replicating and rupturing the cell to release new elementary bodies.PassFinals · original
NAAT sample collectionIllustration of first-catch urine collection in men and vulvovaginal swab collection in women for nucleic acid amplification testing.PassFinals · original
Ascending infection to pelvic inflammatory diseaseDiagram showing spread from endocervical infection through the endometrium to the fallopian tubes, leading to tubal scarring.PassFinals · original

Key sources

  1. BASHH: Chlamydia 2015, including the 26 September 2018 treatment update (BASHH Chlamydia guideline, updated 26 September 2018)Updated 26 Sept 2018
  2. NHS: Chlamydia (NHS symptoms, testing, treatment and partner advice)
  3. UKHSA: National Chlamydia Screening Programme (Current NCSP programme overview and policy)Published 1 Jan 2003 | Updated 6 Jan 2025
  4. UKHSA: NCSP standards (National Chlamydia Screening Programme standards, eighth edition)Published 1 May 2014 | Updated 7 Mar 2022
  5. BASHH: PID 2019 (UK national guideline for the management of pelvic inflammatory disease, with 2019 interim update)Updated 26 Jan 2019
  6. BASHH: Epididymo-orchitis 2020 (UK national guideline for management of epididymo-orchitis)Updated 11 Sept 2020
  7. NICE CKS: Chlamydia – uncomplicated genital (NICE CKS topic)
  8. BASHH position statement on doxycycline use in pregnancy (BASHH Clinical Effectiveness Group position statement)Updated 13 May 2024
  9. BNF: Doxycycline (BNF doxycycline monograph)
  10. BNF: Azithromycin (BNF azithromycin monograph)
  11. UKHSA: Chlamydia re-testing following a positive diagnosis (NCSP routine offer of retesting around 3 months after treatment)Published 23 Jun 2015 | Updated 31 Jul 2019

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.