Chlamydia

Medical information

Written and reviewed by a team of doctors. Dr Fox is regulated by the CQC & GPhC.

Chlamydia is the UK's most common STD

Chlamydia is the most common sexually transmitted disease in the UK, affecting approximately 1 in 12 young people. The highest prevalence is in those aged 15-24 years.

Chlamydia in men is most commonly an infection of the urethra (where urine comes out). In women it is most commonly an infection of the neck of the womb (inside the vagina). Infection can also occur in the anus, mouth, and even eyes.

People who have a Chlamydia infection may not know they have it, particularly women, in whom symptoms are often absent. Most people with an infection are unaware of it.

Chlamydia can cause long term complications. In women this can include pelvic inflammatory disease (PID), tubal infertility, and ectopic pregnancy. Men with active infection may have reduced sperm quality, although this recovers when infection is treated.

Chlamydia is spread mainly by penetrative sexual intercourse, although the exact details are not fully understood. It is considered highly infectious. It can also be spread through oral sex. The infection can sometimes be detected in the conjunctiva of the eyes and in the lining of the mouth, even where there is no genital infection.

The use of condoms, femidoms, and dental dams reduce the chance of infection, but does not eliminate it completely. In many areas the NHS provides free condoms especially if you are under 25 years (see sexual health clinic links below).

Untreated chlamydia sometimes clears on its own, with 50% resolving after 12 months. This is not a reason to delay or avoid treatment.

Confidential chlamydia testing

Sexually active people should test for chlamydia every year and when they have a new partner.

Free chlamydia testing is available at your local NHS Sexual Health Clinic:

• England
• Wales
• Scotland
• Northern Ireland

You may also be able to get chlamydia tests, other STI tests, treatment, and advice through genitourinary medicine (GUM) clinics, family planning clinics, some walk-in centres, and some GPs.

People under 25, and in some areas people over 25, can arrange a test via the National Chlamydia Screening Program.

Postal test kits

A chlamydia test kit can be bought online for delivery by post. Testing is carried out on a urine sample in men, whilst in women testing is carried out on a self-taken vaginal swab.

• Post the sample to the lab in the envelope provided.
• A few days later the result is posted, emailed, or texted back to you.

Testing for other sexually transmitted diseases

Chlamydia infection is often associated with other sexually transmitted diseases. If a chlamydia test is positive, a full range of tests for other sexually transmitted diseases should also be undertaken. This is best done at a specialist sexual health clinic. Some tests take longer to turn positive after you became infected and your local sexual health clinic can also advise about this.

Regular HIV testing should also be carried out for those at increased risk: men who have sex with men; people from sub-Saharan Africa; people who share needles, syringes, or other injecting equipment; and sex workers. See HIV testing guidelines 2020.

Partner notification

It is important if you have tested positive for chlamydia to inform your previous sexual partners from the last 6 months. As chlamydia is often asymptomatic, they themselves may also have it and not be aware. They need testing and possible treatment. If you need help and advice on how to do this, sexual health clinics can arrange anonymous partner notification for you.

Antibiotic chlamydia treatment

Chlamydia is usually treated with the antibiotic doxycycline 100mg taken twice daily for 7 days. This treatment is about 98% effective in eliminating infection. The course of treatment must be completed.

• Avoid sexual contact for the 7 days taking whilst taking doxycycline.
• People with a positive chlamydia test and their sexual partners should be treated, at the same time if possible.
• Tests take 5 weeks to go negative after chlamydia has been successfully treated, but a test of cure is not usually recommended in straightforward infection.
• It is recommended to have another test 3 months after treatment if you are under 25, as it is common to become infected again.

Since 2018, Azithromycin is no longer a recommended first line treatment, as it is less effective in treating more complicated chlamydia and encourages antibiotic resistance in other sexually transmitted infections.

Side effects

Serious side effects of doxycycline are unusual. The most frequent being upset stomach, nausea, and diarrhoea. Less common is benign intracranial hypertension (BIH) with symptoms of headache and blurred vision. Doxycycline can cause light sensitivity. Strong sun and sunbeds should be avoided whilst doxycycline is being taken.

For a full list of side effects please read the doxycycline 100mg patient information leaflet. See also doxycycline page.

Cautions - when NOT to self-treat

Men who have a thick or bloody discharge from the penis with soreness or inflammation, women with heavy offensive vaginal discharge or irregular bleeding and low abdominal pain and men or women, who have anal/rectal discharge (from the back passage) which may be bloody, should not self treat. They should see their regular doctor/GP/GUM clinic for full STI testing as different treatment regimes may be required for other sexually transmitted infections.

Discharge is mucus like fluid coming from the end of the penis, vagina, or anus.

Doxycycline is not suitable for women who are pregnant or breastfeeding, nor people with liver disease, systemic lupus erythematosus, myasthenia gravis, or porphyria.

Alternative treatment

Alternative antibiotics (not available from Dr Fox), include azithromycin and ofloxacin. These antibiotics are an option only in people who cannot take doxycycline. Contact a specialist sexual health clinic, genitourinary medicine clinic, family planning clinic, or GP if you think you need a different treatment.

Chlamydia symptoms

Half of men and the majority of women have no symptoms.

Chlamydia does not usually produce open sores or blisters. If these are present a GP, genitourinary clinic, or sexual health clinic should be consulted.

Women

The majority of infections in women are asymptomatic (without any symptoms). When there are symptoms these could include:

• Increased vaginal discharge
• Unusual vaginal bleeding
• Bleeding between periods
• Heavier periods
• Pain (and/or bleeding) during sex
• Bleeding after sex

Men

Symptoms in men may be so mild as to go unnoticed. Where symptoms are present these could include:

• A white/cloudy or watery discharge from the penis
• Burning and itching in the genital area
• Pain when passing urine
• Painful swelling of the testicles (epididymitis)
• Anal pain and inflamation (proctitis)

Many of these symptoms in men and women can also be caused by other infections and conditions. If you have any of these symptoms get a full check up with a GP, sexual health or genitourinary clinic.

Both men and women: non-genital symptoms

• If the infection is in the rectum/anus there are rarely any symptoms although there can sometimes be discomfort and discharges.
• Infection in the eyes, which is usually a sexually acquired infection, can cause pain, swelling, irritation, and discharge. This can be in one eye or both.
• Infection in the throat isn't common and doesn't usually produce symptoms.

If you think you have non genital chlamydia infection, speak to a GP, sexual health or genitourinary clinic.

Complications and long term effects of infection

Possible complications of infection in women include pelvic inflammatory disease (PID), salpingitis, endometritis, tubal infertility, ectopic pregnancy, sexually acquired reactive arthritis (SARA) (<1%), and perihepatitis.

Complications in men include SARA and epididymo-orchitis.

Antibiotic guardianship

To combat antibiotic resistance please:

• Only use antibiotics when needed
• Never share antibiotics
• Always complete course as instructed
• Take unused medicine to local pharmacy for disposal

Dr Fox supplies chlamydia medication on prescription - you are required to answer a short medical questionnaire before your order can be completed.

Authored 18 February 2010 by Dr Tony Steele
MB ChB Sheffield University 1983. Former hospital doctor and GP.

Reviewed by Dr A. Wood, Dr B. Babor, Dr P. Hunt
Last reviewed 02 November 2020
Last updated 15 October 2021

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