How Do You Know If You Have an STI? Signs, Symptoms, and When to Get Tested

Why symptoms are an unreliable guide

STIs are sometimes called "silent" infections because many cause few or no symptoms for months or years. Chlamydia — the most commonly reported bacterial STI — produces no symptoms in the majority of people who carry it 1Ref 1Workowski KA, Bachmann LH, Chan PA, Johnston CM, Muzny CA, Park I, Reno H, Zenilman JM, Bolan GA (2021).Sexually Transmitted Infections Treatment Guidelines, 2021.Prevalence of asymptomatic chlamydia, gonorrhea, trichomoniasis; screening frequency for MSM; overall STI natural history and testing guidance. Gonorrhea is often symptom-free, particularly in women and in people with throat or rectal infections. HSV (herpes) frequently goes unrecognized because symptoms are mild or mistaken for other skin issues. Even HIV can be silent through a long period after the initial flu-like illness resolves 2Ref 2US Preventive Services Task Force; Owens DK, Davidson KW, Krist AH, et al. (2019).Screening for HIV Infection: US Preventive Services Task Force Recommendation Statement.HIV screening recommendations for adults; silent period after acute HIV infection; importance of at least once-in-lifetime testing.

Waiting for symptoms before getting tested means the infection may silently persist, cause complications over time, and continue to spread to partners. Testing is the only reliable way to know your status.

What symptoms sometimes appear — by infection type

Some patterns are worth knowing, even though they are not reliable for self-diagnosis 1Ref 1Workowski KA, Bachmann LH, Chan PA, Johnston CM, Muzny CA, Park I, Reno H, Zenilman JM, Bolan GA (2021).Sexually Transmitted Infections Treatment Guidelines, 2021.Prevalence of asymptomatic chlamydia, gonorrhea, trichomoniasis; screening frequency for MSM; overall STI natural history and testing guidance:

Bacterial STIs (chlamydia, gonorrhea): Burning with urination, discharge from the penis or vagina, rectal discomfort or discharge. Gonorrhea discharge tends to be thicker and more yellow-green; chlamydia discharge is often clear or white and mild.

Herpes (HSV): Painful blisters or sores that break into ulcers, tingling or burning before a sore appears, flu-like symptoms during a first outbreak 3Ref 3Centers for Disease Control and Prevention (2021).Herpes Simplex Virus — STI Treatment Guidelines 2021 (Web Chapter).Clinical presentation of herpes including blisters, sores, and asymptomatic shedding; testing approach (swab of active sore as most accurate method).

Syphilis: A painless ulcer (chancre) at the exposure site in the first stage; then a rash — often on the palms and soles — and flu-like symptoms in the second stage. Late stages can go symptom-free for years 4Ref 4Centers for Disease Control and Prevention (2021).Syphilis — STI Treatment Guidelines 2021 (Web Chapter).Syphilis stages including painless chancre and secondary rash on palms and soles; rising rates warranting inclusion in routine panels.

HIV: An acute flu-like illness two to four weeks after exposure — then years of no symptoms before immune suppression becomes apparent 2Ref 2US Preventive Services Task Force; Owens DK, Davidson KW, Krist AH, et al. (2019).Screening for HIV Infection: US Preventive Services Task Force Recommendation Statement.HIV screening recommendations for adults; silent period after acute HIV infection; importance of at least once-in-lifetime testing.

HPV: Most strains cause no symptoms. Certain strains cause genital warts; other strains are linked to cervical, anal, and throat cancers and are only detectable by specific screening tests 5Ref 5US Preventive Services Task Force (2018).Screening for Cervical Cancer: US Preventive Services Task Force Recommendation Statement.HPV co-testing with Pap smear for people with a cervix; cancer-causing HPV strains detected through scheduled screening rather than per-exposure testing.

Trichomoniasis: Itching, redness, and a frothy or foul-smelling discharge; often symptom-free 1Ref 1Workowski KA, Bachmann LH, Chan PA, Johnston CM, Muzny CA, Park I, Reno H, Zenilman JM, Bolan GA (2021).Sexually Transmitted Infections Treatment Guidelines, 2021.Prevalence of asymptomatic chlamydia, gonorrhea, trichomoniasis; screening frequency for MSM; overall STI natural history and testing guidance.

Who should get tested — and how often

Testing recommendations vary by your situation 1Ref 1Workowski KA, Bachmann LH, Chan PA, Johnston CM, Muzny CA, Park I, Reno H, Zenilman JM, Bolan GA (2021).Sexually Transmitted Infections Treatment Guidelines, 2021.Prevalence of asymptomatic chlamydia, gonorrhea, trichomoniasis; screening frequency for MSM; overall STI natural history and testing guidance6Ref 6US Preventive Services Task Force; Davidson KW, Barry MJ, Mangione CM, et al. (2021).Screening for Chlamydia and Gonorrhea: US Preventive Services Task Force Recommendation Statement.Annual chlamydia and gonorrhea screening recommendation for all sexually active people under 25 regardless of symptoms:

• New or multiple partners: Test after each new partner, even without symptoms.
• Inconsistent condom use: Higher risk with each unprotected exposure.
• Under 25 and sexually active: Routine annual chlamydia and gonorrhea screening is broadly recommended for this age group regardless of symptoms 6Ref 6US Preventive Services Task Force; Davidson KW, Barry MJ, Mangione CM, et al. (2021).Screening for Chlamydia and Gonorrhea: US Preventive Services Task Force Recommendation Statement.Annual chlamydia and gonorrhea screening recommendation for all sexually active people under 25 regardless of symptoms.
• Men who have sex with men: More frequent screening — every three to six months — is generally recommended, including for rectal and pharyngeal sites 1Ref 1Workowski KA, Bachmann LH, Chan PA, Johnston CM, Muzny CA, Park I, Reno H, Zenilman JM, Bolan GA (2021).Sexually Transmitted Infections Treatment Guidelines, 2021.Prevalence of asymptomatic chlamydia, gonorrhea, trichomoniasis; screening frequency for MSM; overall STI natural history and testing guidance.
• Pregnant: STI screening is a routine part of prenatal care.
• Prior STI: Having had one STI increases the likelihood of another; repeat testing is common practice.

What a standard STI panel includes

STI testing is a menu of tests matched to your exposure history and the types of sex you have had. A basic panel often covers chlamydia and gonorrhea (typically by urine or swab), syphilis (blood test), and HIV (blood or oral swab) 7Ref 7National Library of Medicine (2023).Sexually Transmitted Infection (STI) Tests: MedlinePlus Medical Test.Overview of what a standard STI panel includes and how different tests are performed.

Herpes is not in most routine panels; it requires a specific request, and the most accurate method is a swab of an active sore 3Ref 3Centers for Disease Control and Prevention (2021).Herpes Simplex Virus — STI Treatment Guidelines 2021 (Web Chapter).Clinical presentation of herpes including blisters, sores, and asymptomatic shedding; testing approach (swab of active sore as most accurate method). HPV is detected through cervical Pap and HPV co-testing in people with a cervix — there is no approved HPV test for people with a penis 5Ref 5US Preventive Services Task Force (2018).Screening for Cervical Cancer: US Preventive Services Task Force Recommendation Statement.HPV co-testing with Pap smear for people with a cervix; cancer-causing HPV strains detected through scheduled screening rather than per-exposure testing.

Many STI tests can be done at a primary care office, sexual health clinic, or through telehealth with mail-in kits.

When symptoms do appear, what they might mean

• Discharge, burning, or pelvic discomfort — or no symptoms with recent unprotected sex — raises the question of a bacterial STI (chlamydia or gonorrhea), which are very common in sexually active people under 25 6Ref 6US Preventive Services Task Force; Davidson KW, Barry MJ, Mangione CM, et al. (2021).Screening for Chlamydia and Gonorrhea: US Preventive Services Task Force Recommendation Statement.Annual chlamydia and gonorrhea screening recommendation for all sexually active people under 25 regardless of symptoms.
• Blisters or sores on the genitals, buttocks, or thighs — herpes (HSV), which is more prevalent than most people realize and often goes undiagnosed because symptoms are mild 3Ref 3Centers for Disease Control and Prevention (2021).Herpes Simplex Virus — STI Treatment Guidelines 2021 (Web Chapter).Clinical presentation of herpes including blisters, sores, and asymptomatic shedding; testing approach (swab of active sore as most accurate method).
• A painless genital ulcer or body-wide rash on the palms and soles — syphilis, which has been rising in recent years and is worth including in any panel if you have had new partners 4Ref 4Centers for Disease Control and Prevention (2021).Syphilis — STI Treatment Guidelines 2021 (Web Chapter).Syphilis stages including painless chancre and secondary rash on palms and soles; rising rates warranting inclusion in routine panels.
• Flu-like illness two to four weeks after a high-risk exposure — HIV is worth ruling out by testing; it is the only way to know 2Ref 2US Preventive Services Task Force; Owens DK, Davidson KW, Krist AH, et al. (2019).Screening for HIV Infection: US Preventive Services Task Force Recommendation Statement.HIV screening recommendations for adults; silent period after acute HIV infection; importance of at least once-in-lifetime testing.
• Itching or discharge without sexual exposure — not all genital symptoms are STIs. Yeast infections, bacterial vaginosis, and UTIs can look similar and are not sexually transmitted.