Many STIs in men cause no symptoms at all, which means the only reliable way to know your status is testing. When symptoms do appear, the most common signs include unusual discharge from the penis, pain during urination, sores or bumps on the genitals, and itching or redness in the groin area. But each infection looks and feels different, and understanding those differences helps you figure out what you might be dealing with and how quickly to act.
Most STIs Can Be Silent
The biggest challenge with STIs in men is that many infections produce zero symptoms, sometimes for months or even years. Chlamydia is one of the most common examples. A large percentage of men with chlamydia never notice anything wrong, yet they can still pass the infection to partners and develop complications over time. Gonorrhea is more likely to cause noticeable symptoms in men than in women, but even then, some cases stay quiet. HPV and herpes can also live in your body without producing visible signs.
This is why relying on symptoms alone is unreliable. If you’ve had unprotected sex, a new partner, or multiple partners, testing is the only way to be certain.
Discharge and Pain During Urination
Unusual discharge from the penis is one of the clearest warning signs. With gonorrhea, discharge tends to be yellow, green, or white and often appears within a few days of exposure. Chlamydia can also cause discharge, though it’s typically lighter and less dramatic. Both infections commonly make urination painful or produce a burning sensation.
If you notice any fluid leaking from the tip of your penis that isn’t urine or semen, that’s a strong reason to get tested. The discharge might be subtle, showing up as a small stain on your underwear, or more obvious. Pain or burning when you pee, even without visible discharge, can also signal a bacterial infection in the urethra.
Sores, Blisters, and Bumps
Genital sores are another major category of symptoms, and the type of sore can point toward different infections. Syphilis produces a chancre, which is typically a single, firm, painless sore. Because it doesn’t hurt, men sometimes miss it entirely, especially if it appears in a less visible spot. Herpes, on the other hand, usually shows up as multiple painful blisters that break open and crust over before healing. Herpes outbreaks can also cause blisters around the mouth.
Genital warts caused by HPV look different from both. They tend to be flesh-colored or slightly darker bumps that can appear individually or in clusters resembling cauliflower. They can grow anywhere along the shaft of the penis or on the scrotum, and they may start small (around 5 millimeters) but grow larger over time. Warts are usually painless, though they can become itchy.
Normal Bumps vs. Warts
Not every bump on the penis is an STI. Pearly penile papules are a common, harmless anatomical variation that many men mistake for warts. These are small, dome-shaped bumps that form in neat rows around the head of the penis. They’re generally the same color as your skin or slightly white. Genital warts, by contrast, can appear anywhere on the shaft or scrotum, vary in shape and size, and sometimes cluster together. If you’re unsure what you’re looking at, a healthcare provider can usually tell the difference by appearance alone.
Flu-Like Symptoms and HIV
Acute HIV infection typically develops 2 to 4 weeks after exposure. During this early stage, some people experience flu-like symptoms: fever, headache, rash, sore throat, muscle aches, and swollen lymph nodes. These symptoms can be easy to dismiss as a regular cold or flu, which is part of what makes early HIV so easy to miss. The symptoms usually resolve on their own, but the virus remains active and the infection progresses if untreated.
A flu-like illness a few weeks after a sexual encounter you’re concerned about is worth taking seriously, but plenty of people with acute HIV have mild or no symptoms at all. Again, testing is the definitive answer.
Other Signs to Watch For
Some symptoms are less commonly discussed but still worth knowing about. Anal itching, soreness, or bleeding can indicate an infection transmitted through anal sex. Itching and redness around the groin or genitals may point to trichomoniasis or other infections. Swollen or sore testicles can develop when a bacterial STI like chlamydia or gonorrhea spreads to the epididymis, the tube behind each testicle. Fever, though rare with most STIs, can accompany more advanced infections.
What Happens if You Don’t Get Tested
Untreated STIs in men can lead to serious complications. Bacterial infections like chlamydia and gonorrhea can spread deeper into the reproductive tract, causing infections in the urethra and prostate, swollen and painful testicles, and eventually infertility. HPV can cause cancer in infected tissue, including the penis, throat, and anus. Hepatitis B carries a 25 to 40 percent lifetime risk of liver cancer for those who remain chronically infected. Untreated syphilis progresses through stages and can eventually damage the brain, heart, and other organs. And any untreated STI, including gonorrhea, chlamydia, and herpes, increases your risk of acquiring HIV if you’re exposed to it later.
How Testing Works
STI testing for men is straightforward and varies depending on the infection. Chlamydia, gonorrhea, and trichomoniasis can all be detected through a urine sample. In some cases, a provider may use a swab from the urethra, throat, or rectum, particularly if you’ve had oral or anal sex. Herpes is tested by swabbing an active sore. HIV and syphilis are detected through blood tests, though rapid oral swab tests also exist for HIV.
There is currently no approved test to confirm HPV status in men. Genital warts are diagnosed by visual examination.
When Tests Become Accurate
Getting tested too soon after exposure can produce a false negative because the infection hasn’t built up enough to detect. Each STI has its own testing window:
- Chlamydia and gonorrhea: A urine test or swab catches most infections at 1 week and nearly all by 2 weeks after exposure.
- Syphilis: A blood test catches most cases at 1 month, with nearly all detected by 3 months.
- HIV (blood test): Antigen/antibody blood tests catch most infections at 2 weeks and nearly all by 6 weeks. Oral swab tests take longer, catching most at 1 month and nearly all by 3 months.
If you test negative but tested early in the window, repeating the test after the full window period gives you a more reliable result. For a comprehensive screen after a concerning exposure, many providers recommend testing at 2 weeks for bacterial infections and again at 6 weeks to 3 months for HIV and syphilis to cover all the bases.