How soon after sexual intercourse can you get tested for Sexually Transmitted Infections (STIs)?

STI Testing Timeline After Sexual Exposure

You can begin testing for bacterial STIs (chlamydia and gonorrhea) immediately after sexual exposure, but a comprehensive screening strategy requires follow-up testing at 2 weeks and 12 weeks to account for window periods of different infections. 1

Immediate Testing (Within 72 Hours)

• Nucleic acid amplification tests (NAATs) for chlamydia and gonorrhea can detect infection even within 72 hours of exposure and should be performed at initial presentation 2, 1
• Collect specimens based on exposure sites: urine or genital specimens for vaginal/urethral exposure, rectal specimens for receptive anal intercourse, and pharyngeal specimens for receptive oral sex (gonorrhea only) 2, 1
• Baseline testing should also include syphilis serology (RPR/VDRL and treponemal tests), HIV testing, and hepatitis B serology if unvaccinated 1
• For women, vaginal NAAT for trichomonas is recommended 2

Critical 2-Week Follow-Up Testing

• Repeat testing at 1-2 weeks after exposure is essential for bacterial STIs if initial tests were negative and no presumptive treatment was given, as infectious agents may not have produced sufficient concentrations to be detected initially 2, 3
• This timing is particularly important because even though NAATs can detect infection within 72 hours, the organism load may be below the detection threshold in the earliest days after exposure 3

Definitive 12-Week Testing

• HIV testing at 12 weeks post-exposure (or 8 weeks after completing post-exposure prophylaxis if given) is required to definitively rule out infection, using both laboratory-based Ag/Ab test and diagnostic nucleic acid test (NAT) 1, 4
• Syphilis serology should be repeated at 6-12 weeks if initial testing was negative, as the window period can extend to 1-3 months 1, 3
• For HSV-2, serologic testing should not be repeated until 12 weeks after exposure due to the prolonged window period 3

Reinfection Screening at 3 Months

• If initial chlamydia or gonorrhea tests were positive and treated, retesting at 3 months is mandatory due to high reinfection rates 2, 1
• Reinfection occurs rapidly—within 3.6 months for chlamydia, 6 months for gonorrhea, and 4.8 months for trichomonas in 25% of previously infected individuals 5

Window Period Summary

Understanding these window periods prevents false-negative results and guides the testing schedule 4:

• Chlamydia and gonorrhea: 1-2 weeks 4
• Syphilis: 1-3 months 4
• HIV: 4-12 weeks 4

Post-Exposure Prophylaxis Considerations

• If considering post-exposure prophylaxis, it must be initiated within 72 hours of exposure—doxycycline 200 mg for bacterial STI prophylaxis in men who have sex with men, or antiretroviral therapy for HIV exposure 2, 1
• After 72 hours, this window closes, but screening remains crucial to identify any acquired infection 1

High-Risk Populations Requiring More Frequent Screening

• Individuals with multiple or anonymous partners, substance use during sex, previous STI history, or men who have sex with men should undergo screening every 3-6 months regardless of recent exposures 2, 1, 4
• This more frequent interval (versus annual screening) is justified by the high STI positivity rates of 20% for chlamydia and 17% for gonorrhea found with 2-3 monthly screening in high-risk populations 6

Common Pitfalls to Avoid

• Testing too soon (before 1-2 weeks) for bacterial STIs may yield false-negative results despite active infection 3
• Relying on a single negative test shortly after exposure does not rule out infection 3
• Failing to test at exposure-specific sites (pharynx, rectum) misses a substantial proportion of infections, particularly in men who have sex with men 2
• Assuming condom use eliminates all risk is incorrect, as some STIs transmit through skin-to-skin contact in areas not covered by condoms 3