5 minutes read5 minutes readSummary:
- Chlamydia is called a silent STI because most people who have it don’t get symptoms. Brook says about 75% of women and 50% of men with Chlamydia have no obvious signs.
- Without treatment, it can spread to the womb and fallopian tubes and cause pelvic inflammatory disease (PID), which can affect fertility. A course of antibiotics clears it.
- You can test from 2 weeks after sex. The Better2Know Chlamydia home test checks a urine sample, with results in 2 days.
Chlamydia is the most commonly diagnosed STI in England, yet most people who have it never notice a thing. That’s why it’s often called a silent STI, and why it’s so easy to pass on without knowing.
In this blog, we explain why Chlamydia so often goes unnoticed, which symptoms to look out for, what can happen if it isn’t treated, and when to get tested.
What makes Chlamydia a silent STI?
Most people with Chlamydia don’t have any symptoms. Brook says about 75% of women and 50% of men with Chlamydia have no obvious signs, and UKHSA estimates that 70% to 80% of people with it don’t know they have it.
With nothing to notice, there’s nothing to prompt a test. So the infection can go unnoticed for months and pass on to partners. Some infections clear up on their own, but UK guidelines say only up to half do so within about a year.
How common is Chlamydia?
Chlamydia is the most commonly diagnosed STI in England. UKHSA figures for 2025 show:
- 151,163 Chlamydia diagnoses, almost half (45%) of all new STI diagnoses
- a 10% fall in diagnoses compared with 2024
- relatively high STI diagnosis rates in young people aged 15 to 24
Because so many infections cause no symptoms, the true number of people with Chlamydia is likely to be higher than the number diagnosed.
Can Chlamydia cause symptoms?
If you do get symptoms, they can start from 1 week to several months after infection.
Symptoms in women
- vaginal discharge that isn’t normal for you
- bleeding after sex or between periods
- a burning feeling when you pee
- pain in your lower tummy
Symptoms in men
- white, cloudy or watery discharge from the tip of the penis
- burning and itching around the testicles and penis
- pain and swelling in the testicles
- a burning feeling when you pee
Symptoms in other parts of the body
Chlamydia can also infect the bottom, throat and eyes. It can cause pain, bleeding or discharge from the bottom, a sore throat, or red, painful eyes with discharge. Read more in “Can you get Chlamydia in your eyes?”
What happens if Chlamydia isn’t treated?
The NHS says untreated Chlamydia can lead to:
- pelvic inflammatory disease (PID), an infection of the womb, fallopian tubes and ovaries, which can lead to infertility or an ectopic pregnancy
- an infection in the testicles
- painful joints (reactive arthritis), which usually gets better after a few months
UK estimates suggest that 10% to 17% of women with untreated Chlamydia develop PID. Complications in men are much rarer. If you’re pregnant, Chlamydia can pass to your baby during birth and cause an eye or lung infection, which can be treated with antibiotics.
The World Health Organization also says untreated Chlamydia may make it easier to catch or pass on HIV. Read more in “Can Chlamydia make you infertile?”
Is Chlamydia easy to treat?
Yes. Chlamydia is treated with antibiotics, and UK guidelines recommend doxycycline taken twice a day for 7 days. If you’re pregnant, you’ll be given a different antibiotic.
- Avoid sex, including oral sex, until you’ve finished treatment (or for 7 days if you’re given azithromycin) and any symptoms have gone.
- Your recent partners, usually from the last 6 months, should be tested and treated too.
- If you’re under 25, UK guidelines recommend another test 2 to 6 months after treatment, to check you haven’t caught it again.
Read more in “Can Chlamydia go away on its own?”
When should you get tested?
You can test for Chlamydia from 2 weeks after sex. If you test sooner, the infection may not show up yet, so test again once 2 weeks have passed. If you have symptoms, test straight away. If you have sudden, severe pain in a testicle or severe pain in your lower tummy, get urgent medical care.
Because Chlamydia is so often silent, it’s worth testing:
- when you have a new partner
- after sex without a condom
- if a partner tells you they have Chlamydia
- at least once a year if you’re sexually active
Which test do you need?
Better2Know offers:
- Chlamydia home test: a urine test you take at home, from 14 days after sex, with results in 2 days.
- Peace of Mind: tests for Chlamydia, Gonorrhoea and Syphilis from 14 days after sex, with results in 2 days. You can book it at one of our clinics or order a home test kit.
- Full Screen: tests for 7 infections, including Chlamydia, Gonorrhoea, HIV and Syphilis, from 28 days after sex, with results in 3 days (5 days for the home test).
A urine test checks for Chlamydia in the genitals. If you’ve had anal or oral sex, you may also need a swab from your bottom or throat. If you test before 45 days, a negative HIV result needs a repeat test. A Syphilis test in the first 3 months after sex can miss the infection, so you may need a repeat test. Not sure which test you need? Our Patient Care Team is available 24/7 on 020 7099 0955.
FAQs
Can you have Chlamydia for years without knowing?
Yes. Most people have no symptoms, and only up to half of infections clear on their own within about a year, so it can go unnoticed for a long time. Delaying treatment raises the risk of complications such as PID.
Can you catch Chlamydia from someone with no symptoms?
Yes. You can pass on Chlamydia even if you don’t have symptoms, so a partner who seems well can still have it. Read more in “Can you catch Chlamydia without cheating?”
If my symptoms go away, has Chlamydia gone?
Not necessarily. Symptoms can settle while the infection is still there, so get tested. Read more in “Do Chlamydia symptoms come and go?”
Final thoughts
Chlamydia earns its name as a silent STI because most people never get symptoms. That’s why testing matters: it’s the only way to know, and a short course of antibiotics clears the infection before it can cause problems.
Order a Chlamydia home test or book a test at a clinic near you. Our Patient Care Team is available 24/7 on 020 7099 0955.
About this article
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This article originally appeared on 30 April 2021 and was last updated on 1 October 2026.
This article is general information and not a substitute for personal medical advice.
Sources
- UK Health Security Agency, Sexually transmitted infections and screening for chlamydia in England: 2025 report, 2 June 2026. https://www.gov.uk/government/statistics/sexually-transmitted-infections-stis-annual-data-tables/sexually-transmitted-infections-and-screening-for-chlamydia-in-england-2025-report
- UK Health Security Agency, NCSP: programme overview, updated 24 June 2021. https://www.gov.uk/government/publications/ncsp-programme-overview/ncsp-programme-overview
- NHS, Chlamydia, reviewed 24 October 2024. https://www.nhs.uk/conditions/chlamydia/
- Brook, Chlamydia, accessed 1 October 2026. https://www.brook.org.uk/your-life/chlamydia/
- British Association for Sexual Health and HIV, UK national guideline for the management of infection with Chlamydia trachomatis, 2026. https://www.bashh.org/_userfiles/pages/files/national_guideline_for_the_management_of_infection_chlamydia_trachomatis_2026.pdf
- British Association for Sexual Health and HIV, Summary guidance on testing for sexually transmitted infections, 2023. https://www.bashh.org/_userfiles/pages/files/resources/bashh_summary_guidance_on_stis_testing_2023.pdf
- World Health Organization, Chlamydia, 21 November 2025. https://www.who.int/news-room/fact-sheets/detail/chlamydia
