Post-Visit STI Testing Timeline — What to Test When

Every STI has a window period — the gap between exposure and when a test can reliably detect it. Testing too early produces false negatives that read as reassurance and delay treatment; testing on a rational schedule catches infections at the earliest point they're actually catchable. This guide breaks the post-exposure period into four windows — 72 hours, two weeks, four to six weeks, and three months — and tells you exactly what belongs in each, plus where to get tested without leaving a paper trail at your regular doctor.

The 72-Hour Window: PEP and Doxy-PEP

The first three days after a high-risk exposure are not a testing window — they are a prevention window. Two interventions only work if you start them fast.

HIV PEP (post-exposure prophylaxis) is a 28-day course of antiretrovirals (typically tenofovir/emtricitabine plus dolutegravir or raltegravir) that can prevent HIV seroconversion if started within 72 hours of exposure — ideally within 24. Effectiveness drops sharply after 72 hours and PEP is not offered beyond that point. Sources: sexual health clinics, hospital emergency departments, and travel-medicine clinics in most countries. In the UK it's free through GUM clinics and A&E. In the US, most ERs stock a starter pack. Bring a factual account of the exposure; clinicians need the risk profile to decide whether to prescribe.
Doxy-PEP is a single 200 mg dose of doxycycline taken within 72 hours (ideally 24) of condomless oral, vaginal, or anal sex. Randomized trials (DoxyPEP, DoxyVAC) showed roughly 65-80% reductions in chlamydia and syphilis and around 50% reduction in gonorrhea among MSM and trans women; efficacy data in cis women is weaker. The US CDC issued guidance in 2024 endorsing it for MSM and trans women with a recent bacterial STI. It does nothing for HIV or viral STIs.
Hepatitis B post-exposure prophylaxis — HBIG plus vaccination — is effective if given within 24 hours and useful up to seven days. If you're already fully vaccinated with documented anti-HBs immunity, you're covered.

Do not test for HIV, syphilis, or hepatitis in this window expecting a meaningful result. Nothing detectable has happened yet. The one exception: if you have visible lesions, discharge, or ulcers from a prior exposure, get swabbed now regardless of the clock.

The 2-Week Window: Bacterial STIs by NAAT

Between roughly day 7 and day 14, nucleic acid amplification tests (NAATs) become reliable for the bacterial STIs — the ones that cause most symptomatic infections and are trivially curable if caught. This is the earliest meaningful test date for most travelers.

Chlamydia trachomatis — NAAT is reliable from around 7-14 days post-exposure. Swab or urine sample. Extragenital sites matter: if you had receptive oral or anal sex, you need pharyngeal and rectal swabs, not just urine. Urine-only screening misses the majority of throat and rectal infections.
Neisseria gonorrhoeae — Same 7-14 day window, same site-specific swabbing rule. Ceftriaxone-resistant strains are spreading in parts of Southeast Asia, so if you test positive after travel there, ask the clinic about culture and susceptibility testing on top of the NAAT, because NAAT alone can't guide antibiotic choice for resistant strains.
Trichomonas vaginalis — NAAT from around 5-14 days. Historically under-tested in men; ask specifically if it's not in the panel. Common globally, curable with a single dose of metronidazole or tinidazole.
Mycoplasma genitalium — Rarely included in standard panels but a growing cause of persistent urethritis and cervicitis. If you have symptoms that don't clear on standard treatment, ask for an M. gen NAAT with macrolide-resistance testing. Window is similar: 1-2 weeks.

Two weeks is also the earliest useful window for HIV RNA (NAT) testing, which detects viral genetic material rather than antibodies. RNA turns positive around day 10-14 in most people. It's more expensive than antibody testing and often not part of a standard panel, but if you're anxious and want the earliest reasonable answer, this is it. A negative RNA test at two weeks does not close the window — you still need a follow-up antibody/antigen test later.

The 4-6 Week Window: 4th-Generation HIV, Early Syphilis, Hep B Surface Antigen

This is the window that catches most infections that were missed at two weeks. If you can only test once, testing at six weeks with the right panel picks up the majority of what matters.

HIV 4th-generation antigen/antibody combo test — Detects both p24 antigen and HIV-1/2 antibodies. Reliable in most people by 18-45 days; the CDC considers it conclusive at 45 days for the vast majority. This is the current gold-standard screening test. Rapid fingerstick versions exist but their window is longer (often 90 days) and less sensitive; insist on a lab-processed 4th-gen if you're within the antigen-detection window.
Syphilis serology (treponemal + non-treponemal) — Antibodies typically become detectable at 3-6 weeks after infection, but can take up to 12 weeks. A negative test at six weeks is reassuring but not definitive; if you had a specific high-risk exposure, retest at three months. Any ulcer that appeared 10-90 days after exposure — even a painless one that healed on its own — needs testing regardless of when it appeared.
Hepatitis B surface antigen (HBsAg) — Detectable roughly 4-10 weeks post-exposure. If you're vaccinated and have documented immunity, this is largely academic; if you're not, six weeks is a first-look point and three months is a follow-up.
Hepatitis C RNA — Detectable by PCR from 1-2 weeks; antibody testing lags to 8-11 weeks and can take up to six months. Hep C is now curable with 8-12 weeks of direct-acting antivirals (sofosbuvir/velpatasvir and similar), so catching it early matters.

The 3-Month Window: Definitive Clearance

Twelve weeks is the point at which a clean panel effectively closes the book on a single exposure. Anything that was going to seroconvert has done so by now in essentially all immunocompetent people.

HIV antibody test (any generation) — Definitively negative at 90 days per every major health authority (CDC, WHO, BHIVA, EACS). This is the standard "all clear" endpoint.
Syphilis — Confirmatory retest. If negative at 12 weeks with no symptoms, exposure is effectively ruled out.
Hepatitis B and C antibodies — Full seroconversion by three months in nearly all cases.
HSV-1 and HSV-2 type-specific IgG — Antibody testing for herpes is fraught: false positives at low index values are common, most infected people never seroconvert dramatically, and asymptomatic screening is not routinely recommended. If you develop a suspicious lesion, PCR-swab the lesion directly — that's far more useful than blood serology. If you insist on serology, wait at least 12-16 weeks.

Two things three-month testing does not cover: HPV, for which there is no reliable acute test in men and no meaningful post-exposure testing in women outside routine cervical screening; and mpox, which is diagnosed by PCR of lesion fluid during an active outbreak — there's no "did I get it three months ago" test that matters.

Symptomatic Testing: Don't Wait for the Window

Windows are for asymptomatic screening. If you have symptoms, get seen the same day.

Discharge, dysuria, or pelvic pain within days of exposure — swab and treat empirically for chlamydia/gonorrhea without waiting for results.
Any genital, anal, or oral ulcer — swab for HSV PCR and syphilis darkfield/PCR, and draw syphilis serology, immediately. Painless ulcers are more concerning, not less; a chancre is classically painless.
Fever, rash, sore throat, and lymph node swelling 2-4 weeks post-exposure — this is the acute retroviral syndrome (ARS) presentation of HIV. Request HIV RNA (viral load), not just antibody testing. Standard antibody tests may still be negative during ARS.
Jaundice, dark urine, right-upper-quadrant pain — request full hepatitis panels including HAV IgM (hepatitis A is fecal-oral and common in food/water exposure abroad).

Where to Test Discreetly

Standard options, ranked roughly by privacy:

Mail-in home test kits — Everlywell, LetsGetChecked, myLAB Box, Nurx (US); Better2Know, Randox Health, SH:24 (UK, the last is NHS-funded and free in many regions); iamyours, S.A.M. (parts of EU); DIY HIV self-test kits from pharmacies (widely available). Nothing goes on your primary care record. Positive results still need confirmatory clinic testing. Check that the panel actually covers the extragenital sites you need — many home kits are urine-only.
Dedicated sexual health / GUM clinics — In the UK, GUM clinic records are legally siloed from your GP record unless you consent to share; you can also give a pseudonym at many. In the US, Planned Parenthood, city/county STD clinics, and student health centers offer sliding-scale confidential testing. In much of continental Europe, municipal STI clinics (Checkpoint in Berlin, Zurich, Lisbon, Barcelona; SOA-poli in the Netherlands) offer free or low-cost anonymous testing for MSM and sex workers.
Private walk-in labs — Quest and LabCorp in the US will process direct-to-consumer orders through services like Ulta Lab Tests or Testing.com without a physician referral in most states. Results go to you, not your PCP.
Travel medicine clinics — Often more comfortable handling "I was in [country] and want a full panel" without judgment than a family practice. They also know regional resistance patterns and endemic pathogens (e.g., LGV serovars of chlamydia, tropical ulcer differentials).

Two privacy notes worth knowing. First, insurance claims create paper trails — if you don't want an STI panel on your insurance record, pay cash or use a home kit. Prices for a comprehensive cash-pay panel typically run $150-$400 in the US, £50-£200 privately in the UK, and free through public sexual health services in most of the UK, Australia, and Western Europe. Second, positive results for HIV, syphilis, gonorrhea, chlamydia, and hepatitis B/C are notifiable diseases in most jurisdictions — labs report anonymized aggregate data to public health authorities regardless of where you tested. This is epidemiological surveillance, not a record attached to your name in any database your employer or insurer can see.

A Suggested Test Calendar

If you had a defined exposure and want a clean, defensible testing schedule, this is what most sexual health services would run:

Within 72 hours: Assess for HIV PEP; take doxy-PEP if eligible; hep B PEP if unvaccinated.
Day 10-14: NAAT for chlamydia and gonorrhea at all exposed sites (urine/vaginal, pharyngeal, rectal); trichomonas NAAT; optional HIV RNA if anxious.
Week 6: HIV 4th-generation antigen/antibody; syphilis serology; HBsAg; HCV antibody (add HCV RNA if higher risk).
Week 12: Repeat HIV antibody, syphilis serology, hep B and C serology for definitive clearance.
Any time symptoms appear: Same-day clinic visit, PCR of any lesion, empirical treatment where warranted.

Testing on this schedule catches essentially everything that matters at the earliest medically meaningful point. Testing earlier feels productive but produces false reassurance; skipping the 12-week retest leaves a small but real uncertainty on the table. The calendar is the point.