A syphilis test is a blood test, and diagnosis takes two of them: a screening test (RPR or VDRL, or a treponemal antibody test) followed by a different confirmatory test. Antibodies can take up to two weeks after the first sore appears to show up, so a recent exposure may need a retest CDC lab guidance, 2024.
| Item | Reported cases (babies) |
|---|---|
| 2020 | 2,163 |
| 2021 | 2,881 |
| 2022 | 3,769 |
| 2023 | 3,882 |
How syphilis is tested
Syphilis testing is serology — it looks for antibodies your immune system makes against Treponema pallidum, the spiral-shaped bacterium that causes the infection CDC, About Syphilis. There's no quick swab of a sore in most clinics; the standard is a simple blood draw, and the lab runs it through two separate tests because no single test is reliable on its own.
The two test types measure different things, and you need both to confirm a diagnosis:
- Nontreponemal tests (RPR and VDRL) detect antibodies to material released by damaged cells. They give a titer — a number like 1:8 or 1:32 — that rises and falls with disease activity, which makes them useful for tracking whether treatment worked.
- Treponemal tests (TP-PA, FTA-ABS, EIA, CIA) detect antibodies aimed directly at the bacterium. These usually stay positive for life, even after a cure, so they confirm exposure but can't tell you if an infection is active.
Because a nontreponemal test can flag falsely (from pregnancy, other infections, or autoimmune conditions) and a treponemal test stays positive forever, pairing the two filters out the errors of each. Labs run them in one of two acceptable orders: the traditional algorithm (nontreponemal screen first, then a treponemal test to confirm) or the reverse-sequence algorithm (treponemal screen first, then a quantitative nontreponemal test). Both are valid — your lab decides which to use CDC STI Treatment Guidelines.
When to test after exposure: the window period
Syphilis has a real blind spot early on. The first sore — the chancre — typically appears about three weeks after exposure, with a range of about 10 to 90 days. Antibodies can lag even further behind: a blood test may stay nonreactive for up to two weeks after that sore shows up. So a test done days after a risky encounter can come back negative while the infection is already taking hold.
The practical rule: if your exposure was recent and an early test is negative, don't treat that as the final word — retest. For most people the dependable window falls in the weeks after exposure rather than days. We walk through the timing for syphilis and other infections in detail on our when to test after exposure guide.
This window is exactly why syphilis gets missed. The chancre is usually painless and often tucked somewhere you can't see it — inside the vagina, the rectum, the mouth. It heals on its own in a few weeks, which feels like recovery even though the bacteria are quietly spreading inward. People who never noticed a sore can still test positive months later. If you're trying to match symptoms to stages, see syphilis symptoms in men vs women.
Who should get screened
The U.S. Preventive Services Task Force gives syphilis screening its strongest endorsement, a Grade A, for two groups. The first is everyone who is pregnant: universal, early screening regardless of risk, and if someone wasn't screened early, at the first opportunity — even at delivery USPSTF, pregnancy. The stakes are why this matters so much, covered in syphilis in pregnancy.
For nonpregnant adolescents and adults, the 2022 Grade A recommendation is to screen people at increased risk USPSTF, 2022. That includes:
- Men who have sex with men.
- People living with HIV or who have another STI — and remember, having syphilis roughly doubles the risk of catching HIV.
- Anyone with a history of incarceration or sex work.
- People in communities where syphilis is common.
Geography matters more than people expect. In 2023 the highest primary-and-secondary rates were in South Dakota (about 73 per 100,000), Washington DC (about 40), New Mexico (about 37), and Mississippi (about 30) — several times the national average CDC AtlasPlus, 2023. Syphilis has been climbing for years, with roughly 53,000 primary-and-secondary cases reported in 2023.
Getting tested: the visit, at-home kits, and cost
In a clinic, a syphilis test is one tube of blood from your arm — quick, and usually bundled with other STI screening. Results come back from the lab within days. At-home and order-online kits use a finger-stick blood sample you mail in, then run the same two-test serology in a certified lab. Either way the science is identical; the difference is convenience and privacy.
Cost varies widely by provider, insurance, and whether you go to a public health clinic (often free or low-cost) versus a private lab. If you want to weigh price and turnaround across services, compare testing providers before you commit, or simply get tested through a panel that includes syphilis. A common mistake is ordering a single screening test and stopping at a negative after a recent exposure — build in a retest if your timing was early.
Reading your results
Results depend on which combination of tests came back reactive:
| Screening result | Confirmatory result | What it usually means |
|---|---|---|
| Nonreactive | Not needed | No syphilis detected — but retest if exposure was recent. |
| Reactive (nontreponemal) | Reactive (treponemal) | Active or past syphilis; titer and history guide staging. |
| Reactive (nontreponemal) | Nonreactive (treponemal) | Likely a false positive from another cause. |
| Reactive (treponemal, reverse algorithm) | Nonreactive (nontreponemal) | Possibly treated past infection or very early/late disease — clinician judgment needed. |
The titer number on a nontreponemal test isn't just yes-or-no — it tracks disease activity and, later, confirms cure. A fourfold drop (say 1:32 down to 1:8) over the months after treatment means it worked; a fourfold rise points to reinfection or treatment failure. That's why feeling better isn't proof of cure — the blood titers are.
If your test is positive
Syphilis is curable. Penicillin G given by injection is the preferred treatment for every stage — one shot for early syphilis, three weekly shots for late or unknown-duration disease CDC, latent syphilis. For the full regimen, what the shots feel like, and the expected short flu-like Jarisch-Herxheimer reaction in the first day, see our treatment guide. Also read can you get syphilis again after treatment? — a cure doesn't make you immune, and reinfection is common.
When to see a clinician right away
Some symptoms can't wait for a routine appointment. Syphilis can invade the eyes (ocular syphilis) or the nervous system (neurosyphilis) at any stage — not only late disease StatPearls, neurosyphilis. New vision changes, eye pain, severe headache, confusion, hearing loss, weakness, or trouble walking in someone with known or suspected syphilis is a medical emergency. Don't wait it out; get evaluated the same day.
You should also see a clinician promptly if you've had a known exposure, if a partner tests positive, if you notice any painless sore or unexplained rash (including on the palms or soles), or if you're pregnant and haven't been screened.