A male gets chlamydia through vaginal, anal, or oral sex without a condom with someone who has the infection. The bacteria passes through direct contact with infected mucous membranes or secretions, and about half of men who contract it never develop symptoms, which means you can carry and spread it without knowing.
How Chlamydia Spreads During Sex
Chlamydia is caused by the bacterium Chlamydia trachomatis, which lives in the mucous membranes of the genitals, rectum, and throat. During unprotected sex, the bacteria transfers from one person’s infected tissue to another’s. This can happen through vaginal intercourse (the most common route), anal sex, or oral sex. Ejaculation doesn’t need to occur for transmission. Skin-to-skin genital contact with infected mucous membranes is enough.
Where the infection takes hold depends on the type of sexual contact. Vaginal or insertive anal sex typically leads to a urethral infection in men. Receptive anal sex can cause a rectal infection. Oral sex on an infected partner can lead to a throat infection, though this is less common. You can also have chlamydia in more than one site at the same time.
What the Bacteria Does Inside Your Body
Once chlamydia bacteria reach the lining of the urethra, rectum, or throat, they attach to the surface cells and essentially trick those cells into absorbing them. Within about eight hours, the bacteria shift into a form that can multiply rapidly inside a protected pocket within the host cell. Over the next 48 to 72 hours, the bacteria replicate, eventually bursting out of the cell or being released in a packet to infect neighboring cells.
This cycle of invasion, replication, and cell destruction repeats continuously. If left untreated, the infection can persist for months or even longer than a year. The bacteria’s ability to hide inside your own cells is part of what makes chlamydia so effective at evading your immune system and why so many infections produce no obvious symptoms.
Why Many Men Don’t Notice Symptoms
Roughly 50 percent of men with chlamydia are completely asymptomatic. They feel fine, have no visible signs, and have no reason to suspect an infection. This is the primary way chlamydia continues to spread: people who don’t know they’re infected pass it to partners unknowingly.
When symptoms do appear, they typically show up one to three weeks after exposure. The most common signs in men include a burning sensation during urination, a watery or milky discharge from the penis, and sometimes mild testicular pain or swelling. Rectal infections may cause pain, discharge, or bleeding, but often produce no symptoms at all. Throat infections are similarly quiet, occasionally causing a sore throat but frequently going unnoticed.
Who Faces Higher Risk
Any sexually active male can get chlamydia, but certain factors raise the odds significantly. Having multiple sexual partners, starting a new sexual relationship, and inconsistent condom use are the most straightforward risk factors. A study tracking reinfection rates found that nearly 19 percent of men who were treated for chlamydia became reinfected within six months. Additional factors linked to reinfection included having more than five sexual partners, alcohol use before sex, and having a new partner during the follow-up period.
Men who have sex with men face additional risk because both urethral and rectal infections are common in this group, and rectal chlamydia is almost always asymptomatic. Without routine screening, these infections can persist and spread for long periods.
Testing: What to Know
The standard test for chlamydia in men is a urine sample analyzed with a nucleic acid amplification test (NAAT), which detects the bacteria’s genetic material. If you’ve had receptive anal or oral sex, your provider may also swab the rectum or throat, since a urine test only catches urethral infections.
Timing matters. If you test too soon after exposure, the bacteria may not have replicated enough to be detected. Most infections are detectable within one week, and waiting two weeks catches nearly all cases. If you’ve had a known exposure, testing at the two-week mark gives the most reliable result.
Treatment and Reinfection
Chlamydia is fully curable with antibiotics. The standard treatment is a seven-day course of oral antibiotics, and most people clear the infection completely. You should avoid sexual contact during treatment and for seven days after finishing the medication to prevent passing the infection to anyone else.
Getting treated once does not protect you from getting chlamydia again. There’s no lasting immunity. If your partner isn’t treated at the same time, you can be reinfected as soon as you resume sexual activity. This “ping-pong” effect between untreated partners is one of the most common reasons people test positive again shortly after treatment. Retesting three months after treatment is recommended to catch reinfections early.
How Condoms and Screening Reduce Risk
Consistent condom use during vaginal, anal, and oral sex is the most effective way to reduce your risk. Condoms aren’t perfect, but they dramatically cut transmission rates by creating a barrier between infected mucous membranes and your own tissue.
Because so many chlamydia infections are silent, routine screening is the other critical tool. Sexually active men with new or multiple partners benefit from regular testing even when they feel completely healthy. Catching an asymptomatic infection early prevents complications like epididymitis (a painful inflammation of the tube behind the testicle that can, in rare cases, affect fertility) and stops you from unknowingly passing the infection to others.