Syphilis testing is a simple blood draw that needs two tests to confirm a diagnosis — a nontreponemal screen (RPR or VDRL) and a treponemal test (TP-PA, FTA-ABS, EIA, or CIA). Because antibodies take time to rise, a test can be falsely negative in the first weeks. If the exposure was recent, retest rather than trusting one early negative.
~3 wks; 10–90 days
by stage
| Item | Value |
|---|---|
| Primary sore | painless — ~3 wks; 10–90 days |
| Testing | 2 blood tests |
| Treatment | penicillin — by stage |
| Symptoms fade | ≠ cured |
How syphilis is tested
Syphilis is caused by the bacterium Treponema pallidum, and most testing looks for the antibodies your immune system makes against it rather than the organism itself CDC, About Syphilis. The sample is almost always a vial of blood from your arm. A single result is never enough on its own. A confirmed diagnosis requires two serologic tests of different types, because each one alone produces false positives CDC Lab Recommendations, 2024.
The two families of tests do different jobs:
- Nontreponemal tests — RPR and VDRL. These measure antibodies tied to active infection and are reported as a titer (a number like 1:8 or 1:32) that rises and falls with disease activity, which makes them ideal for tracking response to treatment.
- Treponemal tests — TP-PA, FTA-ABS, EIA, and CIA. These detect antibodies specific to T. pallidum. They confirm the body has met the bacterium at some point, but usually stay reactive for life even after a cure, so they can't tell active from past infection.
Labs combine the two in one of two acceptable sequences. The traditional algorithm runs the nontreponemal test first and confirms a reactive result with a treponemal test. The reverse-sequence algorithm starts with an automated treponemal test (EIA/CIA), then reflexes to a quantitative nontreponemal test. Both are endorsed; which one your lab uses depends on its equipment, not on your case.
When to test after exposure: the window period
Syphilis has a slow onset, and the antibody tests can be nonreactive during the earliest infection. The primary sore, called a chancre, typically appears about three weeks after exposure (incubation runs roughly 10 to 90 days), and antibodies may take up to two more weeks after that sore shows up before a blood test turns positive StatPearls, Syphilis. A test done very soon after a risky encounter can miss a real infection.
A negative test after a recent exposure does not clear you. Retest after the window passes rather than relying on that first result. For the timing logic across different infections, see our guide on when to test after exposure. This window explains many missed cases, though the biology covered next matters more.
Who should get screened
Screening recommendations come from the U.S. Preventive Services Task Force, and two carry its strongest Grade A rating:
- All pregnant people — universal, early screening regardless of risk. If someone wasn't screened early, they should be tested at the first opportunity, even at delivery USPSTF, Pregnancy.
- Nonpregnant adolescents and adults at increased risk — including men who have sex with men, people with HIV or another STI, anyone with a history of incarceration or sex work, and people in higher-prevalence communities USPSTF, 2022.
These recommendations track a real and worsening trend. Primary and secondary syphilis reached about 53,000 reported cases in 2023, and the late or unknown-duration stage roughly doubled — from about 14 to nearly 30 per 100,000 — between 2020 and 2023 CDC AtlasPlus, 2023. It's also unevenly spread: South Dakota, Washington DC, New Mexico, and Mississippi posted the highest primary-and-secondary rates, several times the national average. Congenital syphilis nearly doubled in four years, from 2,163 cases in 2020 to 3,882 in 2023, a 77% rise and the highest level in decades. Untreated syphilis in pregnancy damages the baby in 50 to 80% of cases through stillbirth, prematurity, newborn death, or congenital infection. Prenatal screening plus penicillin stops nearly all of it. For the full clinical picture, read what is syphilis? causes, stages & risks.
Getting tested: what the visit or at-home kit is like
In a clinic, syphilis screening is a quick blood draw added to a standard STI panel — no swab, no special prep, and results usually back within days. At-home kits work the same way, using a finger-stick or mailed blood sample analyzed by a certified lab; a reactive at-home result still needs clinical confirmation and the second test before anyone treats you.
Cost and access vary widely. Many public health clinics offer free or low-cost screening, insurance often covers it for at-risk groups and all pregnant patients, and at-home options have made testing easier for people who can't get to a clinic. You can get tested through several routes, and it's worth comparing turnaround and price — you can compare testing providers before you order. A common, costly mistake is testing too early after a recent exposure and treating a single negative as the all-clear.
Reading your syphilis results
Results hinge on how the two tests line up. Both reactive points to syphilis, current or past. A reactive treponemal test with a nonreactive nontreponemal test often means previously treated or very early/late infection, and the lab usually runs a second treponemal test to sort it out. Both nonreactive means no detectable infection, with the window-period caveat above.
The nontreponemal titer is the number to watch over time. It reflects disease activity: a high titer in active infection, a falling titer after successful treatment, and a rising titer signaling reinfection or treatment failure. Cure is confirmed by that titer. A fourfold drop (for example, 1:32 down to 1:8) over the months after treatment is the goal. The first sore is painless, often hidden, and heals on its own while the bacteria move inward. Later, a non-itchy secondary syphilis rash can appear and also fade without treatment, another false reassurance.
How the two test types compare
| Feature | Nontreponemal (RPR, VDRL) | Treponemal (TP-PA, FTA-ABS, EIA, CIA) |
|---|---|---|
| What it detects | Antibodies tied to active infection | Antibodies specific to T. pallidum |
| Reported as | A titer (e.g., 1:8, 1:32) | Reactive / nonreactive |
| Tracks treatment? | Yes — titer falls with cure | No — usually stays reactive for life |
| Typical role | Screen and monitor | Confirm exposure |
If your result is positive
Syphilis is curable, and penicillin G given by injection is the preferred drug at every stage; the schedule depends on how long you've been infected. For the full regimen, doses, and what the shots are like, see our guide to syphilis treatment CDC STI Treatment Guidelines.
When to see a clinician
Get evaluated promptly if you've had a recent exposure, notice a painless sore or an unexplained rash, or fall into a screening group above. Treat any new vision change or neurological symptom — confusion, severe headache, weakness, hearing loss — as a medical emergency: syphilis can invade the eyes or nervous system at any stage, so ocular and neurosyphilis are not just late problems StatPearls, Neurosyphilis. Having syphilis also roughly doubles the risk of acquiring HIV, one more reason not to wait.