Many STIs in men produce no obvious symptoms at all, which means you can’t reliably tell whether you have one just by how you feel. When symptoms do appear, they typically show up as discharge from the penis, pain during urination, sores or bumps on the genitals, or swelling in the testicles. But the only way to know for certain is to get tested.
Discharge From the Penis
Unusual discharge is one of the most recognizable signs of an infection. It can range from a small, barely noticeable amount to something heavier and more obvious. The color might be clear, white, yellowish, or greenish. You might notice it on your underwear or when you squeeze the tip of your penis.
Here’s the problem: you cannot tell which infection is causing the discharge just by looking at it. Gonorrhea, chlamydia, and trichomoniasis can all produce discharge that looks similar. The World Health Organization’s clinical guidelines confirm that distinguishing between these infections based on the appearance of discharge alone is not possible. A lab test is the only way to identify which one you’re dealing with.
Burning During Urination
A stinging or burning sensation when you pee is a classic sign of urethritis, which is inflammation of the tube that carries urine out of the body. Chlamydia and gonorrhea are the most common STI-related causes. You might also feel like you need to urinate more frequently or more urgently than usual.
This can feel identical to a urinary tract infection, and in fact the two conditions overlap. The key difference is context: if the burning started days to weeks after unprotected sexual contact, an STI is a strong possibility. A urine test can check for both a standard UTI and common STIs at the same time.
Sores, Blisters, and Bumps
Visible changes on or around your genitals are another major category of symptoms, and the type of lesion can point toward different infections.
- Syphilis produces a single, firm, painless sore called a chancre. It typically appears at the spot where the bacteria entered your body and can easily go unnoticed because it doesn’t hurt.
- Herpes looks different. It usually causes multiple small, painful blisters that break open and form shallow ulcers. Outbreaks often come with tingling or burning in the area before the blisters appear.
- Genital warts from HPV start as small, soft, flesh-colored or pinkish bumps. They can appear alone or in clusters and may grow into larger, cauliflower-like shapes over time.
One common source of anxiety: pearly penile papules. These are tiny, smooth, dome-shaped bumps that line up in neat rows around the ridge of the head of the penis. They’re completely harmless, not sexually transmitted, and extremely common. The giveaway is their symmetry. They’re uniform in size and evenly spaced, usually most visible on the top side of the ridge. Genital warts, by contrast, appear in irregular clusters, vary in size, and can show up anywhere on the shaft, head, or surrounding skin.
Scrotal Pain and Swelling
If an STI goes untreated, the infection can travel deeper into the reproductive tract and cause epididymitis, an inflammation of the coiled tube behind each testicle. In men under 40, chlamydia and gonorrhea account for roughly half of all cases.
The pain usually builds gradually rather than striking all at once. It may start as a dull ache in the lower back or side before settling into the scrotum. The affected side often becomes swollen, warm to the touch, and tender. You might also notice urinary symptoms like burning or increased urgency alongside the scrotal pain. This is not something to wait out. Untreated epididymitis can lead to lasting fertility problems.
Flu-Like Symptoms and HIV
Acute HIV infection often looks nothing like what people expect from an STI. Within two to four weeks of exposure, some people develop what feels like a bad flu: fever, headache, body aches, and a rash. These symptoms typically resolve on their own within a week or two, which makes it easy to dismiss them as a passing illness.
After this initial stage, HIV can remain silent for years with no noticeable symptoms. That’s why timing matters. If you develop an unexplained flu-like illness shortly after a high-risk sexual encounter, an HIV test is worth pursuing even if the symptoms go away.
Why You Can’t Rely on Symptoms Alone
A significant number of STIs in men produce no symptoms whatsoever. Chlamydia is the most well-known example. Many men carry and transmit the infection without ever experiencing discharge, pain, or any other warning sign. Gonorrhea can also be silent, particularly when the infection is in the throat or rectum rather than the urethra. Syphilis, HPV, and hepatitis B and C all have stages where you’d feel completely normal despite being infected.
This is why screening based on sexual history matters more than waiting for something to feel wrong. If you’ve had unprotected sex with a new partner, multiple partners, or a partner whose STI status you don’t know, testing is the only reliable way to catch an infection early.
What Testing Actually Involves
For most men, STI testing is straightforward and doesn’t require anything invasive. Chlamydia, gonorrhea, and trichomoniasis can all be detected through a urine sample using a nucleic acid amplification test, which is the current standard. Research comparing urine samples to self-collected penile swabs found that swabs were somewhat more sensitive, catching 94% of chlamydia cases compared to 77% for urine. But urine testing remains widely used because it’s simple and still catches the majority of infections.
If you’ve had oral or anal sex, your provider may recommend throat or rectal swabs in addition to a urine test, since infections in those areas won’t show up in urine. HIV, syphilis, and hepatitis B and C all require a blood draw. Herpes is typically diagnosed by swabbing an active sore, though blood tests for antibodies exist as well.
When to Get Tested After Exposure
Testing too soon after a potential exposure can produce a false negative because the infection hasn’t had time to become detectable. Each STI has its own window period.
- Chlamydia and gonorrhea: Detectable about two weeks after exposure.
- HIV (blood test): A newer antigen/antibody blood test catches most infections by two weeks, with nearly all detectable by six weeks. Oral swab tests take longer, catching most by one month and nearly all by three months.
- Syphilis: A blood test catches most cases at one month and nearly all by three months.
- Hepatitis B: Detectable at three to six weeks.
- Hepatitis C: Catches most cases by two months, with near-complete accuracy at six months.
If your first test comes back negative but was done early in the window period, a follow-up test at the three-month mark gives you the most reliable answer across the board.
Long-Term Risks of Untreated Infections
Beyond the immediate discomfort, untreated STIs carry serious long-term consequences. Gonorrhea bacteria can infect the prostate and trigger chronic inflammation. Research has shown that prolonged, untreated sexually transmitted infections stimulate an inflammatory response in the prostate that, over time, may contribute to more serious conditions including an increased risk of prostate cancer.
Untreated syphilis progresses through stages and can eventually damage the heart, brain, and other organs years after the initial infection. Hepatitis B and C can cause chronic liver disease. And untreated HIV gradually destroys the immune system, progressing to AIDS without treatment. All of these outcomes are preventable with early detection and treatment.