Quick answer: Syphilis is diagnosed with a simple blood test and cured with penicillin — usually a single injection for early infection, or three weekly injections for later-stage infection. Testing is a two-step process (a screening test, confirmed by a second test), and it becomes reliable a few weeks after exposure. After treatment, follow-up blood tests confirm the cure by tracking your "titer" as it falls. It's one of the most treatable STIs — the whole challenge is testing, because it's so often silent.
How syphilis testing works
Syphilis is found through blood tests, not swabs (though a sore can sometimes be tested directly). Testing usually happens in two steps:
- A screening test — commonly RPR or VDRL (called "nontreponemal" tests). These also produce the titer number used to track treatment later.
- A confirmatory test — a "treponemal" test (like TP-PA or FTA-ABS) that confirms a true positive.
Two steps are used because the screening test can occasionally flag a false positive, so a second, more specific test confirms it.
The window period
A test can miss a very recent infection. Syphilis blood tests generally become reliable about 3–6 weeks after exposure. If you test very early and it's negative but you had a real exposure, your clinician may recommend re-testing a few weeks later.
Treatment: penicillin, by stage
The cure is benzathine penicillin G, given as an injection. The number of doses depends on how long you've had it:
| Stage | Typical treatment |
|---|---|
| Early (primary, secondary, early latent — under ~1 year) | One injection |
| Late (late latent, unknown duration, tertiary) | Three injections, one week apart |
| Neurosyphilis (brain/eyes/ears involved) | IV penicillin in hospital, usually 10–14 days |
If you're allergic to penicillin: there are alternatives (like doxycycline) for some stages, but penicillin is so much better — especially in pregnancy and neurosyphilis — that doctors often recommend penicillin desensitization so it can be used safely. Don't let a penicillin allergy stop you from getting treated; talk to your clinician.
What to expect after the shot
Some people get a short-lived reaction within the first 24 hours called the Jarisch–Herxheimer reaction — fever, chills, headache, and muscle aches as the body clears the bacteria. It's usually mild, passes within a day, and is not an allergic reaction. Rest and fluids help.
Confirming the cure: follow-up titers
Unlike some infections, "cured" isn't assumed — it's measured. After treatment you'll have repeat blood tests (typically at 6 and 12 months) to confirm your titer is falling. A fourfold drop (for example, 1:32 down to 1:8) shows treatment worked. We break down exactly what those numbers mean in syphilis RPR titer levels explained.
Partners and re-infection
Your recent sexual partners need testing and treatment too. Avoid sex until your sore(s) are fully healed and treatment is complete — and until partners are treated — so you don't get reinfected. Being cured once does not make you immune; you can catch syphilis again.
Frequently asked questions
Is syphilis curable? Yes — completely, at any stage, with penicillin. Early treatment also prevents the long-term complications of late syphilis.
How long after exposure should I test? Blood tests are generally reliable about 3–6 weeks after exposure. Test sooner if you have symptoms, and re-test if an early test is negative after a real exposure.
Does one shot really cure it? For early syphilis, yes — a single injection. Later-stage infection needs three weekly injections. Follow-up titers confirm it worked.
Can penicillin allergy be worked around? Yes — through desensitization, penicillin can usually still be used safely. It's the preferred cure, so this is worth doing rather than settling for a weaker alternative.
Syphilis testing is quick, the cure is highly effective, and follow-up gives you real proof it's gone. If you've just started this process, you don't have to go through it alone — our community has people who've been exactly where you are.
