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When it might be an STI
For anyone who had sex and is worried, has a symptom, heard from a partner, or just tested positive for a sexually transmitted infection (STI), and for the people beside them. This page passes on, by name, what the Centers for Disease Control and Prevention (CDC) says: why there are often no symptoms, who should be tested and the three ways to do it, where testing is free or low-cost and confidential, six common infections one by one, the steps after a positive test, how to tell a partner, and pregnancy. It builds the questions to ask at a visit. Take only what you need today.
A word with a dotted line under it, like this, opens its official definition, quoted from a U.S. government glossary.
Right now
- Someone made you have sex, or you are not sure you agreed? You are not to blame for what happened. On this site: After sexual assault, with who answers at any hour. In danger now, call 911.
- Worried about HIV after sex or a shared needle? Time matters for that one. It has its own guide here: When it’s HIV.
- Want a test today? CDC’s search finds testing near you: gettested.cdc.gov. CDC says there are many clinics that provide confidential and free or low-cost testing.
- Pregnant? CDC says STI testing should be a part of your prenatal care plan, and to receive treatment right away if you test positive for syphilis.
- Thinking about ending your life? Call or text 988, at any hour.
The first two lines are ours. This page is not for emergencies: for severe pain, a high fever, or anything that frightens you, call 911 or go to an emergency room.
More help
- HIV and hepatitis have their own guides: When it’s HIV and When it’s hepatitis.
- Sex you did not agree to: After sexual assault.
- Someone is threatening to share your pictures: If someone is threatening to share your pictures.
- A partner who frightens you: Make your safety plan.
- No insurance: When you need a doctor and can’t pay.
- Before a visit: Get ready for your appointment.
- Pregnancy: Pregnant, or with a new baby.
- LGBTQ+: LGBTQ+: coming out, staying safe, and people to talk to.
- All our free tools.
This page and its wording were written with AI (Claude) for Scarlet Beast (our AI policy). No doctor, nurse, pharmacist or sexual health worker has reviewed it. The facts were read on October 9, 2026 on the website of the Centers for Disease Control and Prevention (cdc.gov): About Sexually Transmitted Infections (dated March 25, 2024), Getting Tested for STIs (March 17, 2026), How to Prevent STIs (April 9, 2024), Conversation Tips (March 17, 2026), Next steps after testing positive for gonorrhea or chlamydia (April 9, 2024), About STIs and Pregnancy (February 12, 2025), its fact sheets on chlamydia, gonorrhea, trichomoniasis and genital HPV (January 31, 2025), syphilis (January 30, 2025) and genital herpes (February 20, 2024), and the front page of gettested.cdc.gov. CDC is the only source of this guide. The page says when it is passing on CDC’s words, and what is marked “ours” is our own. CDC’s pages say “women” and “men”; where we pass on its lists we kept its words, and the guide is for everyone, whatever your body or your partners. What we left out or did not read: the name and amount of every medicine; CDC’s pages on pelvic inflammatory disease and on doxy PEP (fetched, not used); bacterial vaginosis, Mycoplasma genitalium, pubic lice, scabies and mpox; its treatment guidelines for clinicians; what each state lets a person under 18 consent to; what an insurance statement shows; how health departments notify partners; and prices. We ran no search on gettested.cdc.gov and called no number. It saves nothing and loads no tracking.