A syphilis test on Koh Samui is usually a simple blood test, either a quick finger-prick or a sample from a vein sent to a lab. It can usually find syphilis from about 3–6 weeks after infection, and a repeat test at around 3 months confirms a negative result.
Syphilis is treatable with antibiotics, especially when found early. The hard part is that its signs are easy to miss, so testing matters.
What is syphilis?
Syphilis is a bacterial infection passed on through close skin contact with a sore during vaginal, anal or oral sex. Because sores can be on skin that a condom does not cover, condoms lower the risk but do not remove it.
It develops in stages. Each stage can look very different, and some have no signs at all. The WHO fact sheet on syphilis describes it as a preventable bacterial infection that can be treated with antibiotics. Having it once does not protect you from getting it again.
Syphilis symptoms by stage
Not everyone notices every stage. Some people only find out from a routine blood test, which is one reason regular testing is useful.
Stages of syphilis: signs, timing and testing
| Stage | Typical timing | Common signs | What testing shows |
|---|---|---|---|
| Primary | About 3 weeks after infection (range roughly 10–90 days) | Usually a single painless sore where the infection entered; heals in a few weeks | Blood tests may still be negative early; a swab of the sore can help |
| Secondary | A few weeks to a few months later | Rash, often on palms and soles; flu-like feelings; mouth patches; patchy hair loss | Blood tests are usually reactive |
| Early latent | Within about the first year, no signs | None | Blood tests reactive; only testing finds it |
| Late latent | After about a year, no signs | None | Blood tests reactive |
| Tertiary | Many years later, if never treated | Damage to the heart, brain, nerves or other organs | Blood tests plus further checks |
Syphilis can also affect the eyes, ears or nervous system at any stage. Sudden changes in vision or hearing with a possible exposure need a doctor quickly.
The sore that goes away
A key worry is a painless sore that healed on its own. Healing does not mean the infection has gone. Without treatment, syphilis moves into the next stage, so it is still worth testing.
When to test for syphilis
Blood tests look for antibodies, which take a few weeks to develop. Testing the week after sex is usually too early to rule it out.
- With a sore or rash: see a doctor now, whatever the timing.
- After a risk with no signs: a test from about 4–6 weeks catches most infections.
- To confirm a negative: repeat the test at around 3 months (12 weeks).
Many people combine syphilis testing with their HIV checks, as the timing is similar. Our guide to the HIV window period explains the HIV side, and when to get an STD test after unprotected sex covers the full timeline across infections.
Types of syphilis test
Syphilis testing uses two families of blood test. Doctors often use both, because together they show whether an infection is current or from the past.
Syphilis test types and what each tells you
| Test | What it detects | Result time | What it tells you |
|---|---|---|---|
| Rapid syphilis test (finger-prick) | Treponemal antibodies | About 15–30 minutes | A quick screen; a reactive result needs lab confirmation |
| Lab treponemal test (such as TPHA, TPPA or EIA) | Treponemal antibodies | Same day to 2 days | Shows you have had syphilis at some point; often stays positive for life |
| Non-treponemal test (RPR or VDRL) | Antibodies linked to active infection, measured as a level | Same day to 2 days | Helps show if infection is current and tracks the response to treatment |
| Swab of a sore (PCR, where available) | Bacteria in the sore | About 1–3 days | Useful very early, before blood tests turn positive |
Why a test can stay positive after treatment
Treponemal tests often remain reactive for life, even after successful treatment. That does not mean the infection is back. Doctors use the RPR level over time to check that treatment worked, so keep a copy of your results if you have had syphilis before.
What your results mean
- Non-reactive (negative): no sign of syphilis, as long as the test was not too early.
- Reactive on a rapid or treponemal test: a lab test, usually including RPR, confirms whether it is current.
- Reactive RPR with a reactive treponemal test: usually a current infection needing treatment.
A doctor will assess your situation, including your history, before any diagnosis. If treatment is needed, it is usually antibiotics, and partners should be tested too.
Syphilis, HIV and pregnancy
Syphilis sores can make it easier to catch or pass on HIV, which is why doctors usually suggest testing for both together. If you could be pregnant, testing is especially important. Untreated syphilis can pass to a baby during pregnancy, and early treatment greatly lowers that risk. Tell the doctor if you are pregnant or trying to be.
Typical syphilis test prices
These are typical market ranges from published clinic prices in Thailand in 2026. Prices change, so treat them as a guide and message us for our current price.
Syphilis test prices (typical 2026 ranges)
| Option | What it includes | Typical range (THB) |
|---|---|---|
| Doctor consultation | Review of symptoms and history | About 500–1,000 |
| Rapid syphilis test | Finger-prick treponemal screen | About 400–800 |
| Lab syphilis tests | Treponemal test and RPR | About 500–1,500 |
| Rapid combination screen | HIV, syphilis and hepatitis B and C | About 2,000–2,500 |
See our guide to typical STD test prices on Koh Samui for full packages.
Syphilis testing on Koh Samui
Our confidential HIV and STI testing service offers syphilis blood tests, and results are explained in plain language. If you have a sore, tell us when you message, so the doctor can plan the right test.
Tips for your visit
- Bring any earlier syphilis results, especially if you were treated before.
- Ask to add HIV testing. Our guide to HIV testing on Koh Samui explains the options.
- If you had oral or anal sex, consider chlamydia and gonorrhoea testing with the right swabs.
People on HIV PrEP on Koh Samui usually have syphilis tests at their three-monthly check-ups, which catches silent infections early.
Frequently asked questions
How soon after sex does syphilis show on a test?
Most infections show on a blood test from about 3–6 weeks. A repeat at around 3 months confirms a negative result.
Is a rapid syphilis test accurate?
It is a good screening test once enough time has passed. A reactive result always needs a lab test to confirm it.
Can syphilis go away on its own?
The sore and rash can fade, but the infection usually stays without treatment. Testing is the only way to know.
Why is my test still positive after treatment?
Treponemal tests often stay positive for life. Your doctor checks the RPR level instead to see whether treatment worked.
Should my partner get tested?
Yes. Partners should be tested and, if needed, treated, so the infection is not passed back and forth.
Book a confidential syphilis test
A syphilis test on Koh Samui is quick, and early results make treatment simpler. A doctor can look at your timing and any signs and suggest the right test. You can message a doctor privately on WhatsApp to arrange a confidential syphilis test.