Chlamydia

What is chlamydia?

Chlamydia is a bacterial sexually transmitted infection (STI), among the most frequently diagnosed anywhere, caused by the Chlamydia trachomatis bacteria. Antibiotics clear it up reliably, but leaving it untreated can allow more serious problems to develop over time.

What are the symptoms of chlamydia?

Chlamydia often produces no noticeable signs whatsoever, which is part of why it spreads so easily without people realising. Where symptoms do appear, they usually start somewhere between a week and a few months after infection.

In women, or anyone with a vagina, possible symptoms include:

• discharge that seems different from usual
• bleeding between periods, or after intercourse
• discomfort or stinging while urinating
• pain low down in your tummy.

In men, or anyone with a penis, possible symptoms include:

• a discharge from the penis that looks different from normal
• soreness or itching around the penis and testicles
• discomfort or stinging while urinating.

Chlamydia can also affect anywhere else that comes into contact with infected fluid, causing pain, bleeding or discharge from the bottom, a sore throat, or red, sore, weepy eyes.

What are the causes of chlamydia and who is at risk?

Chlamydia bacteria travel in semen and vaginal fluid, most often passing between people during sex without a condom, whether that's vaginal, anal or oral.

Genital-to-genital contact alone can pass it on, even without penetration or ejaculation, and it can also spread through infected fluid on shared, unwashed sex toys, or by touching infected fluid and then your eye. A pregnant woman with chlamydia can pass it to her baby during birth.

Anyone who's sexually active can get chlamydia, though your risk climbs with a new partner or a wider number of partners recently. It's also diagnosed more often in people under 25, and becomes less likely wherever condoms are used consistently.

Are there different types of chlamydia?

The type most people mean by "chlamydia" is a genital infection that's easily treated and, while common, rarely causes lasting harm if caught early.

A rarer variant, lymphogranuloma venereum (LGV), comes from specific strains of the same bacterium and behaves more aggressively, sometimes causing genital ulcers, swollen lymph nodes, or inflammation around the back passage, alongside cramping and fever.

A separate strain again causes trachoma, a serious eye disease spread through contact with eye or nose discharge rather than sex. It's a leading cause of preventable blindness in parts of the world with limited access to clean water and sanitation, but is not something most people in the UK need to worry about.

How is chlamydia diagnosed?

Testing is straightforward – either a urine sample, or a swab taken from wherever infection is suspected, such as inside the vagina, the tip of the penis, the throat or the back passage. You can often take the swab yourself, and won't necessarily need an internal examination.

The most reliable lab test looks for the bacteria's genetic material, and results are usually back within a few days. You can also request a chaperone for any physical examination, and self-test kits are available for people without symptoms who still want to check, including free kits for under-25s in some areas.

How is chlamydia treated?

Antibiotics clear the infection, most often a week-long course of doxycycline, or either a single dose or 3-day course of azithromycin – the latter antibiotic is generally preferred if you're pregnant.

Sometimes treatment starts before your results are back, particularly if you've been in contact with someone who has a confirmed infection.

You'll usually notice things improving within a week, but it's important to finish the whole course, even if your symptoms clear up sooner.

You'll need to avoid vaginal, anal and oral sex until both you and any partner have completed treatment and are clear of infection, which typically means waiting at least 7 days after finishing your antibiotics.

When should I see a doctor?

It's worth getting checked promptly if either you or someone you've slept with suspects an infection, if a recent encounter wasn't protected by a condom, or if you're expecting a baby, or hoping to be, and there's a chance you've been exposed. A GP or sexual health clinic can arrange this.