References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Chlamydia is the most commonly diagnosed bacterial STI in the UK. It’s most common in people under 25, particularly women. Because it’s usually silent, many more cases go undiagnosed than are detected. The National Chlamydia Screening Programme encourages annual testing for sexually active young people.
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UK Trends
| Fact | Detail |
|---|---|
| Most common bacterial STI | Highest diagnosis rates of any bacterial STI |
| Peak age | 15-24 year olds |
| Screening programme | Annual screening recommended for under 25s |
| Asymptomatic rate | Up to 70-80% have no symptoms |
Why Chlamydia Is So Common
- Often silent — people don’t know they have it
- Easily transmitted through unprotected sex
- Young people are sexually active with new partners
- Testing isn’t always taken up
Who Is Most Affected
- Sexually active women under 25
- Men under 25
- People with new or multiple partners
Testing and Treatment
- Simple urine or swab test
- Home kits widely available and often free
- Treated with doxycycline 7 days
- Partners treated simultaneously
Why Testing Matters
- Prevents PID, infertility and ectopic pregnancy
- Stops transmission to partners
- Annual screening is easy, free and confidential
Read more: What is chlamydia? | Home chlamydia tests | UK STI rates
Frequently Asked Questions
How common is chlamydia really?
The most frequently diagnosed bacterial STI in the UK.
Who should test?
All sexually active people under 25, at least yearly.
Is it curable?
Yes — easily with a short course of antibiotics.
Related reading
- Can You Get Chlamydia From Kissing?
- Can You Have Chlamydia and Test Negative?
- Multi-Site STI Testing: Genital, Rectal and Throat
- What Is Mycoplasma Genitalium?
- Abnormal Genital Discharge and Chlamydia
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
