Chlamydia is the most common bacterial sexually transmitted infection in the United States, and roughly half of men who have it don’t know it because they have no symptoms at all. In 2024, over 564,000 cases were reported in men alone. The infection is caused by bacteria that target the lining of the urethra, rectum, or throat, and while it’s easily curable with antibiotics, leaving it untreated can quietly damage your reproductive health.
How Men Get Chlamydia
Chlamydia spreads through vaginal, anal, or oral sex without a condom with someone who has the infection. The bacteria don’t need to cause symptoms in your partner to be contagious. Once they reach the cells lining your urethra or rectum, they enter those cells, multiply inside them over about 48 to 72 hours, and then burst the cell open to release new bacteria that infect neighboring cells. This cycle repeats, spreading the infection locally while often producing little or no noticeable irritation.
You can be infected at more than one site at the same time. A urethral infection from vaginal or oral sex and a rectal infection from receptive anal sex are the most common, but throat infections also occur. Each site can transmit the bacteria independently, which means testing at just one location can miss an active infection elsewhere.
What Chlamydia Feels Like in Men
About 50 percent of men with chlamydia never develop symptoms. When symptoms do appear, they typically show up within one to three weeks after exposure. The most common signs are:
- Burning during urination, often mistaken for a urinary tract infection
- Discharge from the penis, usually clear or slightly cloudy, and lighter than what gonorrhea produces
- Pain or swelling in one or both testicles, which can range from a dull ache to sharp tenderness
Rectal infections have their own set of symptoms: pain, discharge, and sometimes bleeding. Many rectal infections are also silent, though, which is why testing based on sexual history matters even if nothing feels wrong.
The fact that symptoms are often mild or absent is what makes chlamydia so effective at spreading. You can carry and transmit the bacteria for months without realizing it, which is why routine screening is so important for sexually active men, particularly those with new or multiple partners.
How Chlamydia Is Diagnosed
The standard test is a nucleic acid amplification test, or NAAT, which detects the bacteria’s genetic material with high accuracy. For a urethral infection, you’ll provide a urine sample. The key detail: it needs to be a “first-catch” sample, meaning you collect urine from the very beginning of your stream, not midstream like a typical urinalysis. You’ll also need to avoid urinating for at least two hours before the test so enough bacteria accumulate to be detected.
If you’ve had receptive anal or oral sex, your provider may also swab your rectum or throat. These sites won’t show up on a urine test, so mentioning your full sexual history helps ensure nothing gets missed.
What Happens If It Goes Untreated
The most well-known complication in men is epididymitis, an infection of the coiled tube behind each testicle that stores and carries sperm. It causes swelling, heat, and pain in the scrotum that can become severe. Left untreated further, the inflammation can scar the reproductive tract.
More recently, researchers have found a direct link between chlamydia and male infertility that goes beyond epididymitis. Scientists at the Hudson Institute of Medical Research discovered chlamydia bacteria in testicular tissue biopsies from men who were infertile but had never been diagnosed with an STI and reported no symptoms. Blood tests confirmed 12 out of 18 of those men had antibodies showing past exposure to the bacteria. Preclinical studies in mice supported the finding: chlamydia established chronic infections in the testes that significantly impaired normal sperm development. This suggests the bacteria can silently reach the testes and disrupt fertility without ever producing obvious symptoms.
Chlamydia also increases your vulnerability to HIV. The inflammation it causes in urethral or rectal tissue creates an easier entry point for the virus if you’re exposed.
How Chlamydia Is Treated
Uncomplicated chlamydia is cured with a seven-day course of an antibiotic taken twice daily by mouth. This regimen is the current first-line recommendation from the CDC, replacing the older single-dose approach, which studies showed had a higher failure rate in men, particularly for rectal infections.
A single-dose alternative still exists for situations where completing a full week of medication isn’t realistic, but it comes with a trade-off: lower cure rates and often a need for follow-up testing to confirm the infection cleared. Your provider will help determine which option makes more sense for your situation.
During treatment, you should avoid sex for seven days after starting the antibiotic (or seven days after a single-dose treatment) to prevent passing the infection to a partner. Finishing the entire course matters even if symptoms disappear in a day or two, because the bacteria can survive at low levels and bounce back.
Getting Your Partners Treated
Anyone you’ve had sex with in the past 60 days needs to know they may be infected and should get treated, even without a positive test result. If that conversation feels difficult, many states allow a process called expedited partner therapy, where your clinician provides extra medication or a prescription that you can give directly to your partner without them needing a separate clinic visit. This is particularly useful for reaching partners who might not seek care on their own.
Skipping this step is one of the main reasons people get reinfected almost immediately after treatment. If your partner isn’t treated and you resume having sex, the bacteria come right back.
Retesting After Treatment
The CDC recommends retesting three months after your diagnosis, regardless of whether your symptoms resolved and whether you believe you were reinfected. Repeat infections are common, and retesting at this interval catches them early before complications develop or you unknowingly pass the bacteria to someone new. This three-month window applies to all men treated for chlamydia, not just those who had symptoms initially.
If you test too soon after treatment (within a few weeks), residual bacterial DNA can trigger a false positive even though the live infection is gone. The three-month mark hits the sweet spot: enough time for dead bacteria to clear, but soon enough to catch a new exposure.