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Health condition · Clinically reviewed

Chlamydia, testing, doxycycline and telling partners - the calm version.

The UK's most common bacterial STI - often silent, easy to test for, and quick to treat if you know where to look. Free and confidential testing is widely available.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against BASHH, NICE and the National Chlamydia Screening Programme.

  • 03

    Current for 2026

    Reflects BASHH 2015 chlamydia guidance and the 2024 update - doxycycline first-line, azithromycin reserved.

Key facts

Chlamydia at a glance.

The essentials in plain English - what it is, how common it is, and how it is diagnosed and treated in UK sexual health services.

  • What it is

    A genitourinary infection caused by the bacterium Chlamydia trachomatis - the most common bacterial STI in the UK.

  • How common

    Over 200,000 diagnoses each year in England, with the highest rates in people under 25.

  • Symptoms

    Often silent - around 70% of women and 50% of men have no symptoms at all.

  • Screening

    The National Chlamydia Screening Programme (NCSP) offers free tests to under-25s and their partners.

  • First-line therapy

    Doxycycline 100 mg twice daily for 7 days - superior to azithromycin for rectal and LGV infection.

  • Complications

    Untreated chlamydia can cause pelvic inflammatory disease, tubal infertility, ectopic pregnancy and chronic pelvic pain.

Why this guide matters

Silent, common - and simple to treat.

Chlamydia rarely announces itself. The three points below shape how UK sexual health services find it, treat it and stop it spreading.

  • Testing is the only reliable finder

    Because most infections are silent, screening (not symptoms) is what turns up most cases - especially under 25.

  • Doxycycline works, and quickly

    A week of doxycycline clears the infection - the exception is LGV, which needs three weeks.

  • Partner treatment prevents ping-pong

    Testing and treating recent partners stops re-infection and interrupts community spread.

How the diagnosis is made

From first test to treatment and follow-up.

The steps a UK GUM clinic, GP or online sexual health service will normally follow, in order - so you know what to expect and why.

  1. 01

    Assessing

    Sexual health history

    A confidential discussion of symptoms, partners, contraception and past STIs - the foundation of a proper risk assessment.

  2. 02

    Assessing

    Site-specific NAAT sampling

    Nucleic acid amplification test - first-catch urine in men, vulvovaginal swab in women (self-taken preferred), plus rectal or pharyngeal swabs per exposure.

  3. 03

    Assessing

    Full STI screen offered

    HIV, syphilis, gonorrhoea and hepatitis B and C testing - plus a pregnancy test where relevant.

  4. 04

    Confirming

    LGV testing where indicated

    Men who have sex with men with rectal chlamydia are tested for lymphogranuloma venereum serovars L1 to L3.

  5. 05

    Confirming

    Examination for complications

    Assessment for pelvic inflammatory disease, epididymo-orchitis, proctitis or reactive arthritis where symptoms suggest it.

  6. 06

    Preparing

    Partner notification

    Contact tracing for partners in the past 6 months, or longer for regular partners - offered discreetly by GUM or online sexual health services.

  7. 07

    Preparing

    Confidential care pathway

    GUM clinics and Sexual Health London online provide free, confidential testing and treatment outside a GP record where preferred.

Typical timeline: test to treatment in days, not weeks.

Symptoms

What chlamydia can look like.

Most infections cause no symptoms at all. When they do, the pattern depends on the site of exposure - genital, rectal, pharyngeal or ocular.

  • Often no symptoms at all

    Around 70% of women and 50% of men have no symptoms - screening is the only way to find it.

  • Urethritis in men

    Dysuria, clear or cloudy urethral discharge, testicular pain or epididymitis are the classic male features.

  • Vaginal and pelvic symptoms

    Discharge, intermenstrual or postcoital bleeding, deep dyspareunia, dysuria and pelvic pain may occur - see our pelvic inflammatory disease guide.

  • Rectal chlamydia

    Usually silent, but can cause proctitis with anorectal pain, discharge and tenesmus - LGV serovars L1 to L3 cause severe proctocolitis.

  • Pharyngeal infection

    Throat infection is nearly always asymptomatic and only found on targeted swabbing after oral exposure.

  • Ocular and neonatal disease

    Adult conjunctivitis, trachoma (a leading global cause of blindness) and neonatal conjunctivitis or pneumonia acquired at birth.

  • Reactive arthritis

    A post-infective arthritis that can follow chlamydia - see our ankylosing spondylitis guide for the wider spondyloarthritis family.

  • Red flag - LGV bubo or PID

    Painful inguinal swelling in men who have sex with men, or severe pelvic pain with fever, needs urgent GUM assessment.

Treatment

How chlamydia is treated in the UK.

Doxycycline first-line for uncomplicated infection, azithromycin in pregnancy, three weeks of doxycycline for LGV, and combination therapy for PID.

  • Doxycycline 100 mg bd for 7 days

    First-line for uncomplicated genital and rectal chlamydia - better cure rates than azithromycin, especially at rectal sites.

  • Azithromycin 1 g stat + 500 mg od 2 days

    Alternative regimen where doxycycline is not suitable - historical single-dose monotherapy is no longer preferred due to emerging resistance.

  • Pregnancy - azithromycin

    Azithromycin 1 g stat is the preferred pregnancy regimen. Amoxicillin 500 mg tds or erythromycin 500 mg qds for 7 days are alternatives.

  • LGV - doxycycline 21 days

    Lymphogranuloma venereum requires doxycycline 100 mg twice daily for a full three weeks.

  • PID regimen

    Pelvic inflammatory disease is treated with combination therapy - ofloxacin plus metronidazole, or ceftriaxone plus doxycycline plus metronidazole.

  • Neonatal chlamydia

    Erythromycin for 14 days with ophthalmology input for conjunctivitis or pneumonia acquired at birth.

  • Partner notification and treatment

    Mandatory contact tracing - all recent partners should be tested and treated even if asymptomatic. Abstain until seven days after treatment.

  • Test of cure and re-screen

    Selective test of cure at 3 to 6 weeks (pregnancy, rectal or LGV infection, persistent symptoms). Repeat screening at 3 months given high re-infection rates.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP or a GUM clinician knows your history and can tell you which parts apply to you. If in doubt, get tested.

  • BASHH. UK national guideline for the management of infection with Chlamydia trachomatis (2015, updated 2024).

  • NICE CKS. Chlamydia - uncomplicated genital.

  • UK Health Security Agency. National Chlamydia Screening Programme standards.

  • BASHH. UK national guideline for the management of lymphogranuloma venereum (LGV).

Red flags

When chlamydia needs urgent attention.

Most infections are simple to treat. These are the situations where a specialist opinion, an urgent GUM slot or a safeguarding conversation is needed.

  • Suspected PID

    Lower abdominal pain, deep dyspareunia, abnormal bleeding or fever needs same-day assessment - untreated PID scars the fallopian tubes.

  • Fitz-Hugh-Curtis syndrome

    Right upper quadrant pain with pelvic infection suggests perihepatitis - a chlamydial complication needing urgent review.

  • Epididymo-orchitis

    Acute testicular pain and swelling in a sexually active man is chlamydia until proven otherwise - and needs to be distinguished from testicular torsion.

  • LGV in men who have sex with men

    Painful inguinal bubo or severe proctitis warrants prompt LGV testing and 21 days of doxycycline.

  • Pregnancy and neonatal risk

    Untreated chlamydia in pregnancy can cause preterm birth, low birth weight and neonatal conjunctivitis or pneumonia - treat promptly.

  • Ectopic pregnancy risk

    A history of chlamydia raises ectopic risk - any positive pregnancy test with pelvic pain needs urgent early pregnancy assessment.

  • Reactive arthritis

    New joint pain, urethritis and conjunctivitis after chlamydia (Reiter triad) needs rheumatology and GUM review.

  • Suspected sexual assault

    Any concern about non-consensual exposure should be routed through a Sexual Assault Referral Centre (SARC) for holistic support.

  • Under-16 disclosure

    A positive test in a young person triggers a safeguarding conversation using Fraser and Gillick principles.

Living with it

A treatable infection, with a clear plan.

Four things that make the biggest difference day to day - finishing the course, waiting the week, telling recent partners and re-testing at three months.

A quiet reminder

Regular screening is the quiet superpower.

Home postal kits, NCSP under-25 screening and Sexual Health London make testing routine - and routine testing is what stops the long-term harms.

  1. 01 Treatment

    Finish the course

    Complete the full 7 days of doxycycline (or 21 for LGV) - stopping early risks treatment failure and onward transmission.

  2. 02 Abstinence

    Wait 7 days after treatment

    Avoid sex - including oral - for at least a week after starting treatment, and until all partners have been treated.

  3. 03 Partners

    Tell recent partners

    Contact tracing feels awkward but prevents re-infection and long-term harm. Anonymous partner notification is available online.

  4. 04 Re-test

    Repeat screening at 3 months

    Re-infection is common - a repeat test at three months catches new exposures before complications develop.

Frequently asked

Everything we get asked about chlamydia.

Quick, confidential answers on testing, treatment, partners and complications.

  • What is chlamydia?

    Chlamydia is a sexually transmitted infection caused by the bacterium Chlamydia trachomatis. It can infect the genitals, rectum, throat and eyes, and is the most common bacterial STI in the UK with over 200,000 diagnoses each year.

  • How would I know if I had chlamydia?

    Often you would not - around 70% of women and 50% of men have no symptoms at all. That is why free testing is offered to everyone under 25 through the National Chlamydia Screening Programme and to any adult with a new partner or symptoms.

  • How is chlamydia tested?

    A nucleic acid amplification test (NAAT) is the gold standard - a first-catch urine sample in men and a self-taken vulvovaginal swab in women. Rectal and throat swabs are offered based on the type of sex you have had.

  • What is the current treatment for chlamydia?

    BASHH first-line treatment is doxycycline 100 mg twice daily for 7 days. Azithromycin is used in pregnancy or when doxycycline is not suitable. LGV needs 21 days of doxycycline, and PID needs combination antibiotics.

  • Do my partners need to be treated too?

    Yes - all sexual partners in the past six months should be tested and treated, even if they have no symptoms. Sexual Health London and GUM clinics offer discreet partner notification and free treatment.

  • Can chlamydia cause infertility?

    Untreated chlamydia can lead to pelvic inflammatory disease, which scars the fallopian tubes. Around 10 to 15% of women with PID develop tubal infertility, and the risk of ectopic pregnancy also rises. Early treatment prevents these complications.

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