What Is Chlamydia? Symptoms, Testing and Treatment

Sexual health is part of everyday self-care, but it's often the part that slips. Chlamydia shows why: it's one of the most common STIs, it usually causes no symptoms, and so people carry it for months without knowing, passing it to partners along the way. This guide explains what chlamydia is, how it spreads, what it can do if it's missed, and how testing and treatment work. Ovio's chlamydia test is done at home in Bangkok.

What Is Chlamydia?

Chlamydia is an infection caused by the bacterium Chlamydia trachomatis (often shortened to CT). It's the most commonly diagnosed bacterial STI in the world. It can infect the cervix, the urethra (the tube urine passes through), the rectum, the throat and the eyes.

According to the World Health Organization (WHO), there were an estimated 128.5 million new chlamydia infections among adults worldwide in 2020. It's most common in young adults, but anyone who is sexually active can get it, whatever their age, gender or sexuality.

Why Is Chlamydia Called a Silent Infection?

Chlamydia can only live inside human cells. It enters the cells that line the genital tract, rectum or throat and multiplies there slowly. The inflammation it causes is usually low-grade, so it rarely brings on sudden pain or fever. Most people feel completely well.

That's what makes it easy to spread and easy to miss. Without testing, an infection can go on for months, and the quiet inflammation can damage the reproductive organs in the meantime. For more on infections like this, see STIs without symptoms.

How Is Chlamydia Spread?

Chlamydia lives in genital fluids and on the moist linings of the body. It passes on through contact with infected fluids, which can happen with:

• Vaginal or anal sex without a condom, including when there are no symptoms.
• Oral sex, which can pass chlamydia to or from the throat.
• Genital contact without penetration, if fluids are exchanged. Ejaculation isn't needed.
• Shared sex toys that aren't washed or covered with a new condom each time.
• Infected fluid getting into the eye, causing conjunctivitis.
• From mother to baby during birth, which can cause eye infections and pneumonia in newborns.

Chlamydia isn't spread by kissing, hugging, sharing towels or cups, swimming pools or toilet seats.

Chlamydia Symptoms in Women and Men

Most people with chlamydia have no symptoms. When they do appear, it's usually one to three weeks after sex, and they're often mild enough to ignore.

In women

• A change in vaginal discharge, such as more than usual or a different colour or smell
• Pain or burning when passing urine
• Bleeding between periods or after sex
• Pain in the lower abdomen, or pain during sex

In men

• Burning or stinging when passing urine
• A white, cloudy or watery discharge from the tip of the penis, often noticed in the morning
• Irritation at the opening of the penis
• Pain or swelling in one testicle

In the rectum, throat or eyes

Rectal infections are usually silent but can cause pain, discharge or bleeding. Throat infections rarely cause anything noticeable. In the eyes, chlamydia causes redness, soreness and discharge.

These symptoms overlap with gonorrhoea and other infections, so a test is the only way to know. See chlamydia vs gonorrhoea for how the two compare.

Complications of Untreated Chlamydia

Left untreated, chlamydia can spread and cause lasting damage, often without warning signs along the way. In women it can move up to the womb and fallopian tubes and cause pelvic inflammatory disease (PID). Scarring of the tubes can lead to long-term pelvic pain, ectopic pregnancy and infertility; untreated chlamydia is one of the leading preventable causes of infertility. In men it can spread to the tube behind the testicle (epididymitis), causing painful swelling. Inflammation from any STI also makes it easier to catch or pass on HIV.

How Is Chlamydia Treated?

Chlamydia is curable with antibiotics. International guidelines recommend doxycycline for 7 days as the first choice, with alternatives such as azithromycin when doxycycline isn't suitable. Pregnant people are given an antibiotic that's safe in pregnancy. Most people are cured with one course.

• Finish the whole course, even if you feel fine after a couple of days.
• Avoid sex, including oral sex, until you and your partners have finished treatment and for 7 days after.
• Tell recent partners, so they can be tested and treated even without symptoms. Otherwise the infection passes straight back to you. If you're not sure how to start that conversation, see what to do if your partner tests positive for an STI.
• Retest after about three months, because reinfection is common. See STI retesting after treatment.

When Should You Get Tested for Chlamydia?

Chlamydia tests look for the bacterium's genetic material, and it takes time for there to be enough to detect. NHS services recommend testing two weeks (14 days) after the sex you're worried about. A test taken a few days after can miss an infection that's still developing. Work out your own dates with the STI test window calculator.

If you have symptoms, don't wait: test straight away, and your doctor may suggest a repeat test later. Test once a year if you're under 25 and sexually active, and whenever you have a new partner or a partner tells you they have an STI.

How Is Chlamydia Diagnosed?

Chlamydia is found with a nucleic acid amplification test (NAAT), usually called PCR. It's highly accurate on the right sample, and none of the samples hurt:

• First-catch urine: the first part of the stream, rather than midstream. The usual test for men, and an option for women. It tests the urethra only.
• Vaginal swab: the most sensitive sample for women. Swabs taken by the person themselves are about as accurate as those taken by a clinician.
• Throat or rectal swab: needed after oral or anal sex, because a urine test can't detect an infection in those places.

Because chlamydia and gonorrhoea often occur together, they're usually tested from the same sample. For how urine tests, swabs and blood tests compare across STIs, see STI blood test vs urine test vs swab.

Chlamydia Testing in Bangkok

Chlamydia testing is available at public and private hospitals and clinics across Bangkok. Whether you live here or are visiting, regular testing is simply part of looking after yourself.

If you'd prefer to keep it private, Ovio's at-home STI testing brings a doctor to your home, condo, hotel or office at a date and time you choose, for Thai and international clients. The doctor takes the urine sample and any swabs you need. A chlamydia test (PCR) is ฿2,990, or ฿3,990 for chlamydia and gonorrhoea together from one sample. If the result is positive, the doctor will explain it and the treatment you need. Not sure what else to test for? See which STI tests should I get?

Frequently Asked Questions

Can chlamydia go away on its own?

Sometimes the body clears it, but you can't count on that, and while it lasts it can damage the reproductive organs and spread to partners. Treatment is quick and simple, so always treat a positive result.

How long after sex do chlamydia symptoms appear?

When symptoms appear, it's usually one to three weeks after sex. But most people never get symptoms, so the absence of symptoms doesn't mean you're clear.

Can you get chlamydia from oral sex?

Yes. Chlamydia can pass to the throat, or from the throat to the genitals, though this is less common than with vaginal or anal sex. A throat swab is needed to find it. See STIs from oral sex.

Can I get chlamydia again after treatment?

Yes. Having had chlamydia doesn't make you immune, and reinfection from an untreated partner is common. That's why partners need treatment and you should retest after about three months.

Is a chlamydia test a blood test?

No. Chlamydia is diagnosed with a PCR test on a urine sample or a swab, not a blood test. Blood tests for chlamydia antibodies can't tell whether you have an infection now.