Most sexually transmitted infections don’t cause obvious symptoms, so you can’t rely on how you feel to know whether you have one. Across major STIs like chlamydia, gonorrhea, and trichomoniasis, roughly 50 to 60% of infections produce no noticeable signs at all. The only reliable way to know your status is to get tested. That said, your body does sometimes send signals worth recognizing.
Symptoms That Can Point to an STI
When symptoms do show up, they tend to fall into a few recognizable patterns. The most common include unusual discharge from the penis or vagina, painful or frequent urination, sores or warts on the genitals, itching and redness in the genital area, and abnormal vaginal odor. Some infections also cause blisters or sores in or around the mouth, anal itching or bleeding, lower abdominal pain, or fever.
Internal symptoms are easier to miss. Pain during deep penetration, pelvic cramping, or unexpected bleeding during sex can all signal an underlying infection. These are particularly common with chlamydia and gonorrhea, which can travel deeper into the reproductive tract without causing the kind of external symptoms you’d spot on your own.
Different infections also look different on the skin. A syphilis sore is typically a single, painless, firm bump. Herpes lesions, by contrast, usually appear as multiple painful blisters that may cluster together. This distinction matters because a painless sore is easy to dismiss or miss entirely, especially if it appears in a spot that’s hard to see, like inside the vagina or around the anus.
Why You Can’t Rely on Symptoms Alone
The high rate of silent infections is the core problem. In a large meta-analysis of women tested for chlamydia, about 61% had no symptoms at all. For gonorrhea, that figure was 53%. For trichomoniasis, 57%. Men tend to notice gonorrhea symptoms more often (burning during urination, discharge), but chlamydia in men is also frequently silent. HIV and syphilis can go months or years without producing anything noticeable.
This means you could feel perfectly fine and still carry an infection that’s transmissible to partners and, over time, damaging to your own body. The absence of symptoms is not the same as the absence of infection.
What Happens If an STI Goes Untreated
Untreated chlamydia and gonorrhea can lead to pelvic inflammatory disease (PID) in women, a condition where infection spreads to the uterus, fallopian tubes, or ovaries. PID causes scar tissue to form inside and around the fallopian tubes, which can block them entirely. One in 8 women with a history of PID has difficulty getting pregnant. PID also raises the risk of ectopic pregnancy, where a fertilized egg implants outside the uterus, a potentially life-threatening situation. The longer treatment is delayed, the more likely these complications become.
In men, untreated infections can cause painful inflammation in the tubes near the testicles, which can also affect fertility. Untreated syphilis progresses through stages over years and can eventually damage the heart, brain, and other organs. Untreated HIV gradually destroys the immune system.
How STI Testing Works
Testing is simpler than most people expect. For chlamydia and gonorrhea, the standard test uses a urine sample or a swab (vaginal, cervical, throat, or rectal, depending on the type of sex you’ve had). These tests use a method called nucleic acid amplification, which detects genetic material from the bacteria. It’s highly accurate.
HIV, syphilis, and hepatitis B and C are detected through blood tests. Herpes is a bit different: there’s no routine screening for it. A blood test for herpes antibodies exists, but the CDC recommends it mainly for people with recurrent or unexplained genital symptoms, those whose partner has herpes, or people living with HIV. If you have an active sore, a swab of that sore is the most accurate approach.
At-home test kits have become widely available. FDA-approved kits for chlamydia and gonorrhea achieve 95 to 99% accuracy when used correctly. The key word there is “FDA-approved.” Unregulated kits can produce unreliable results, so check for that designation before ordering.
When to Get Tested After Exposure
Testing too early after a potential exposure can produce a false negative. Each infection has a window period, the time it takes for the test to reliably detect it.
- Chlamydia and gonorrhea: Urine or swab tests are generally accurate about 2 weeks after exposure.
- Syphilis: A blood test catches most infections at 1 month, and almost all by 3 months.
- HIV (blood test): An antigen/antibody blood test catches most infections at 2 weeks and almost all by 6 weeks. An oral swab test takes longer: most by 1 month, almost all by 3 months.
- Hepatitis B: Detectable at 3 to 6 weeks.
- Hepatitis C: A blood test catches most infections at 2 months and almost all by 6 months.
If you test negative but your exposure was recent, retesting after the full window period has passed gives you a more definitive answer.
Who Should Be Getting Tested Routinely
You don’t need symptoms or a known exposure to have a good reason to test. The CDC recommends routine chlamydia and gonorrhea screening for all sexually active women under 25, and for older women with risk factors like a new partner or multiple partners. All pregnant women should be screened for syphilis, HIV, and hepatitis B. Men who have sex with men should be tested at least annually for syphilis, chlamydia, gonorrhea, and HIV. Anyone with 10 or more lifetime sexual partners is considered higher risk and may benefit from broader screening, including herpes testing if symptoms are present.
For cervical cancer screening related to HPV, women aged 30 to 65 are recommended to get a Pap test every 3 years, or a combined Pap and HPV test every 5 years.
What to Do If You Test Positive
Bacterial infections like chlamydia, gonorrhea, and syphilis are curable with antibiotics. Trichomoniasis, caused by a parasite, is also curable. Treatment is straightforward for most people, often a single dose or a short course of medication. Viral infections like herpes, HIV, and hepatitis B are not curable but are manageable with medication that controls symptoms and reduces transmission risk.
One practical concern people overlook: your sexual partners need to know and get treated too, or the infection will pass back and forth. In 48 states plus Washington, D.C., a system called expedited partner therapy allows your clinician to prescribe medication for your partner without requiring them to come in for a separate visit. This removes a significant barrier, since many partners won’t or can’t schedule their own appointment quickly. If you’re uncomfortable with a direct conversation, many health departments also offer anonymous partner notification services that contact your partners without revealing your identity.