01 · Overview
The short version
No symptoms does not rule out an STI
Many STIs cause no symptoms or only mild ones, especially early on. An infection can still be passed to another person even when you feel normal.
The test depends on the exposure
Urine, blood, and swab tests all have a role, but they do not check the same things. Mouth, anal, and genital exposure may need different sample sites.
Treatment depends on the germ
Antibiotics can cure many bacterial and parasitic STIs. Viral STIs are usually not cured, but treatment can still ease symptoms and lower spread.
Prevention works best in layers
Condoms, dental dams, vaccination for HPV and hepatitis B, testing before new partners, and fewer partners can all lower risk. No single step removes risk completely.
02 · Care guidance
When to get help
Emergency help
- Call 911 or go to the ER now for chest pain, trouble breathing, fainting, signs of stroke, severe allergic reaction, sudden severe pelvic pain with possible pregnancy, or confusion with fever and severe illness.
Get advice promptly
- Contact a clinician promptly if you have new genital sores, unusual discharge, pain when peeing, pelvic pain, pain after sex, a partner with an STI, or any possible exposure and you are pregnant.
- Seek urgent medical advice the same day for testicular pain, because sudden pain can be an emergency and should not be watched at home.
If you had a new or higher-risk sexual exposure but no symptoms, ask about STI testing as soon as practical. If you were treated, ask when to avoid sex again and whether your partner also needs testing or treatment.
03 · Sexually Transmitted Infections
What an STI is, and how it spreads
STIs are infections spread mainly through sexual contact, but some also pass through skin-to-skin contact or from parent to baby.
An STI is an infection that can spread during vaginal, oral, or anal sex. Some infections move through skin-to-skin contact, which is why herpes and HPV can spread even when penetration does not happen. A few infections can also pass during pregnancy or childbirth, and some can spread through breastfeeding, blood transfusion, or sharing needles.
Different germs cause different STIs. Bacteria, viruses, and parasites can all be involved, so the name of the infection matters. Chlamydia, gonorrhea, syphilis, trichomoniasis, genital herpes, HIV, HPV, and pubic lice are a few examples. The likely symptoms, the test used, and the treatment plan are not the same for each one.
- STI is the infection; STD is the disease that may develop if the infection is not treated.
- One person can have more than one STI at the same time.
- The type of exposure helps decide what testing is needed.
04 · Sexually Transmitted Infections
Symptoms that should make you think about testing
Symptoms can be mild, absent, or easy to confuse with a urinary, skin, or vaginal problem.
Common STI symptoms include unusual discharge, sores or blisters, warts, itching, redness, pain or burning when peeing, pelvic or belly pain, anal soreness or bleeding, abnormal vaginal odor, and fever. But many infections do not cause symptoms at all, especially early. That is why a person can have an STI and pass it on without knowing.
Symptoms are clues, not a diagnosis. Burning with urination can also come from a urinary tract infection, dehydration, skin irritation, or a yeast infection. Itching or redness can come from friction, soaps, allergies, or other infections. A sore can be from an STI, but it can also be from something else. Testing is how clinicians sort this out.
- A negative symptom check does not rule out an STI.
- Worsening pain, sores, or discharge should not be ignored.
- Symptoms in one person do not predict symptoms in their partner.
05 · Sexually Transmitted Infections
How testing is chosen
The right test depends on the infection being considered and where the exposure happened.
Clinicians may use a swab from a sore, the vagina, penis, anus, or mouth. Blood tests can diagnose some infections, including HIV and syphilis. Urine is used for some tests, but urine alone does not check for every STI and does not cover every exposed body site.
That is why mouth or anal sex may need site-specific testing, not just a urine test. If you ask for testing, it helps to say what kind of contact happened and whether there were symptoms, rather than naming only one infection. A negative test can be helpful, but only for the infections and sites that were actually checked.
- Testing can be needed even when there are no symptoms.
- Swab, urine, and blood tests are not interchangeable.
- A focused exposure history helps choose the right panel.
06 · Sexually Transmitted Infections
Treatment and why partners matter
Treatment works best when it matches the cause and includes partner care when needed.
Antibiotics can treat many STIs caused by bacteria or parasites. Viral STIs usually are not cured, but antiviral medicine can often help with symptoms and lower the chance of spreading infection. The medicine depends on the diagnosis, not just on how the symptoms feel.
It is important to ask when sex should be avoided after treatment. That timing matters because some infections can be passed back and forth between partners if both people are not treated or if sex starts again too soon. A partner may need testing or treatment even if they feel fine, since many STIs cause no symptoms.
- Do not share leftover antibiotics or use someone else’s treatment.
- Partner treatment can prevent reinfection.
- Do not guess the medicine from symptoms alone.
07 · Sexually Transmitted Infections
Ways to lower the chance of getting or passing an STI
The safest plan combines barrier protection, vaccination, testing, and honest communication.
The surest way to avoid an STI is not to have vaginal, oral, or anal sex. If you do have sex, condoms used correctly every time lower the risk, but they do not remove it completely. That is especially true for infections that spread by skin-to-skin contact. Dental dams can help during oral sex, and internal condoms are another option for some people.
Testing before sex with a new partner, fewer partners, and mutual monogamy after both partners have been tested can also lower risk. Vaccination for HPV and hepatitis B is another important layer of protection. Alcohol and drugs can make safer choices harder in the moment, so avoiding them during sex may help.
- Condoms reduce risk, but no method is perfect.
- Vaccines matter for HPV and hepatitis B.
- Safer sex works better when both partners are honest about testing.
08 · Sexually Transmitted Infections
STIs during pregnancy
Pregnancy changes the stakes, so exposure should be discussed promptly.
Some infections can be more serious during pregnancy or can affect the fetus or newborn. Problems can include preterm birth, low birth weight, serious illness, birth defects, or lifelong disabilities such as hearing loss or learning problems. Not every infection causes harm, but some do, so it is safer to speak up early than to wait and wonder.
If you are pregnant and think you may have been exposed to an STI, contact your prenatal clinician promptly. Some medicines are safe in pregnancy and some are not, so treatment needs medical guidance. Regular prenatal care helps find and treat infections early.
- Tell your prenatal clinician about any possible STI exposure.
- Do not assume a medicine is safe in pregnancy without checking.
- Condoms can still lower risk during pregnancy.
09 · FAQ
Questions people ask
Are all STIs curable?
No. Antibiotics can cure many bacterial and parasitic STIs, but viral STIs are usually not cured. Even when a cure is not possible, treatment can still reduce symptoms and lower spread, so getting the right diagnosis still matters.
Do condoms prevent STIs completely?
No. Condoms lower the risk a lot, especially when used correctly every time, but they do not remove the risk entirely. That is because some STIs spread through skin-to-skin contact around areas a condom does not cover.
How soon should I get tested after a new exposure?
As soon as practical after a new or higher-risk exposure, especially if you have symptoms or a partner has an STI. The exact timing can depend on the infection and the test, so a clinician may also tell you when a repeat test is needed.
Can STIs affect pregnancy?
Yes. Some infections can affect the pregnant person, the fetus, or the baby. If you are pregnant and may have been exposed, contact your prenatal clinician promptly because the safest treatment choices can be different during pregnancy.
What if my partner tells me they have an STI?
Avoid sex until you know what testing or treatment you need, and get medical advice about next steps. You may need testing even if you feel fine, because many STIs do not cause symptoms.
Can I trust a home test kit instead of seeing a clinician?
Sometimes a home test can help, but it may not cover every infection or every exposed body site. If your exposure included oral or anal sex, symptoms are present, or you are pregnant, a clinician visit is safer because the test choice matters.
10 · References
References and supporting evidence
These sources support the points identified below. Source checking is not clinical approval.
- S1: Sexually Transmitted InfectionsMedlinePlus / U.S. National Library of Medicine
Explains the basic definition of STIs, that they can spread through sexual contact, that symptoms may be absent, how diagnosis can use swabs or blood tests, treatment categories, and prevention measures like condoms, testing, and vaccination.
- S2: Teen Sexual HealthMedlinePlus / U.S. National Library of Medicine
Explains silent infection risk, teen sexual health prevention basics, condom use, dental dams, HPV vaccination, testing before sex, and the role of healthy communication and mutual monogamy.
- S3: Infections and PregnancyMedlinePlus / U.S. National Library of Medicine
Explains that infections in pregnancy can affect the pregnant person and fetus, that some medicines are safe while others are not, and that prompt prenatal care helps find and treat infections early.
General information, not a diagnosis. This guide is not a substitute for care from a qualified healthcare professional. For an emergency, call 911 in the US or your local emergency number. Illustrations are conceptual and are not diagnostic images.