Chlamydia

Medical information

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 to 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 vigina). Infection can also occur in the anus, mouth, and even eyes.

People who have the infection may not know they have it, particularly women, in whom symptoms are often absent. Most people with 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 infection is often associated with other sexually transmitted diseases. In men who have sex with men there is an increased risk of HIV. If a chlamydia test is positive, a full range of tests for other sexually transmitted diseases should be undertaken.

Chlamydia is spread mainly by penetrative sexual intercourse, although the exact details are not fully understood. It is considered highly infectious. It can 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 reduces the chance of infection, but does not eliminate it completely.

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 self-testing

• Sexually active people should test every year and when they have a new partner. Annual HIV testing should also be carried out for those at risk.
• A chlamydia test kit can be ordered through the 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, or emailed back to you.

People under 25, and in some areas people over 25, can arrange a test via the National Chlamydia Screening Program. GPs, genito-urinary medicine clinics, and some walk-in centres can provide tests and treatment.

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 whilst taking doxycycline and for 7 days afterwards, until no longer infectious.
• 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.

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 sun beds should be avoided whilst doxycycline is being taken.

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

Cautions - when not to self-treat

Men who have a thick or bloody discharge from the penis with soreness or inflammation and women with heavy offensive vaginal discharge or irregular bleeding and low abdominal pain should see their regular doctor. 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 in people who cannot take doxycycline.

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 or genitourinary 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)

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.

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 treatment 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
Last updated 16 August 2019

Reviewed by Dr B. Babor, Dr A. Wood, Dr P. Hunt
Last reviewed 25 June 2019