Syphilis test
Note: this site is for informational purposes only. To view test results or book a test, use the NHS app in England or contact your GP.
The syphilis test checks whether you have been infected with the bacterium Treponema pallidum. Syphilis is a sexually transmitted infection that is easy to treat with antibiotics but can cause serious health problems if left untreated. Testing is simple and usually involves a blood sample and sometimes a swab.
Who needs this test
You may need a syphilis test if:
- you have a sore, ulcer, or unusual rash on your genitals, mouth, or throat
- you have been told that a sexual partner has syphilis
- you are being tested or treated for another sexually transmitted infection (STI) such as gonorrhoea, chlamydia, or HIV
- you are pregnant — syphilis testing is offered to all pregnant women in the UK as part of routine antenatal care
- you have had unprotected sex and are concerned about your sexual health
- you have symptoms that may be secondary syphilis, such as a skin rash, fever, or swollen glands
- you need to monitor the success of syphilis treatment
All people who are pregnant are offered a syphilis blood test early in pregnancy as part of routine care. You may be offered a second screening test later in pregnancy if you are at risk of getting infected after your first test.
You can get tested at a sexual health clinic (also called a genitourinary medicine or GUM clinic), your GP surgery, or some community services. You do not need a referral to attend a sexual health clinic.
Preparing for your test
No special preparation is needed for a syphilis blood test.
If you have a sore or ulcer, the doctor or nurse may take a swab from it. You do not need to prepare for this either.
If your doctor thinks the infection may have affected your nervous system, they may arrange a lumbar puncture (spinal tap) to test the cerebrospinal fluid (CSF) — the fluid that surrounds the brain and spinal cord. Your doctor will explain how to prepare for this if it is needed.
Understanding your results
What the test measures
Syphilis is caused by a bacterium (germ) called Treponema pallidum. Most syphilis tests look for your body’s response to the infection. Sometimes if there is a sore or ulcer that can be swabbed a PCR test that looks for DNA from the bacteria is used. Different types of test are used depending on the stage of infection and what the laboratory is trying to find out.
In the UK, laboratories usually follow a two-step process. First, a screening test is used. If this is positive further tests are carried out to confirm the result and identify the stage of infection. A repeat blood sample is usually requested to confirm any new positive result.
Types of syphilis test
Treponemal tests (such as EIA, CLIA, TPHA and TPLA)
These tests look for antibodies that are directed specifically at the Treponema pallidum bacterium. They are more specific than non-treponemal tests and are less likely to give a false positive result. Some of these tests can become positive within two to four weeks of infection.
Once positive, treponemal tests usually remain positive for life, even after successful treatment. This means they cannot be used on their own to tell whether someone has a current or past infection
Non-treponemal tests (RPR)
This test looks for antibodies that are produced in response to syphilis infection but is not specifically targeted at the bacterium itself. These antibody levels fall with successful treatment, which makes these tests particularly useful for monitoring whether treatment is working.
Direct detection tests
If you have a sore or ulcer, the doctor may take a swab or scraping for one of the following:
- Dark-ground microscopy: the sample is examined under a specialist microscope to look directly for the bacteria. This requires expert handling and is done less frequently now.
- PCR (polymerase chain reaction): this test looks for the genetic material (DNA) of the bacterium in a swab from the sore. It is sensitive and specific but is not available at all laboratories in the UK.
A syphilis test result is not always straightforward. The result depends on the stage of infection, the type of test used, and your individual circumstances. Your doctor or sexual health team will explain your result and what it means for you. Do not try to interpret a syphilis result on your own.
Negative result
A negative result usually means no syphilis infection has been detected. However, antibodies may not appear in the blood until several weeks after infection. If you were recently exposed to syphilis, you may need to return for a repeat test. Your doctor or sexual health team will advise you on timing.
Positive screening result — awaiting confirmation
If your initial screening test is positive, the laboratory will automatically carry out additional tests before releasing a final result. A positive screening test does not always mean you have syphilis — false positives can occur. You will usually be asked to give a repeat blood sample to confirm the finding.
Confirmed positive result
A confirmed positive result means you have been infected with syphilis. The type of tests that are positive, and the levels of non-treponemal antibodies, help your doctor understand the stage of infection:
- Primary syphilis: a sore (chancre) which is normally painless appears at the site of infection, usually within 10 days to three months of exposure. Some antibody tests may still be negative at this very early stage.
- Secondary syphilis: if untreated, the infection spreads through the bloodstream. Commonly, a skin rash (which is usually not itchy), fever, sore throat, and swollen glands can occur two to twelve weeks after the sore appears. A range of other symptoms affecting many parts of the body can also occur during secondary syphilis. Antibody tests are reliably positive at this stage.
- Latent syphilis: the infection is present but causes no symptoms. This stage can last for years. It can only be detected through blood testing.
- Late (tertiary) syphilis: if syphilis is not treated for many years, it can eventually cause serious damage to the brain, heart, blood vessels, eyes, bones, and nervous system. This stage develops in a minority of untreated cases.
False positive result
Non-treponemal tests can occasionally give a false positive result in some other conditions, including pregnancy, lupus, Lyme disease, some viral infections, and in people who use intravenous drugs. This is why a positive screening result is always confirmed with a second test.
Some people who have grown up in certain tropical regions may have been infected by very similar infections (yaws, pinta, bejel). These are not sexually transmitted and syphilis tests cannot tell the difference between syphilis and these infections.
Monitoring treatment
After treatment, your doctor will arrange follow-up blood tests. Non-treponemal antibody levels (such as RPR) should fall steadily if treatment has been successful. A fall in these levels confirms your recovery. Treponemal tests often remain positive for life even after a cure, so they are not used to monitor treatment response.
Questions to ask your doctor
What happens next
If your result is negative and you have no symptoms or recent exposure, no further action is usually needed. If there is a possibility of very recent infection, your doctor may ask you to return for a repeat test up to 3 months later.
If your result is positive, syphilis is treated with antibiotics — most commonly penicillin given by injection. Infections caught early can usually be cured with a short course of treatment. If you have late syphilis, you may need a longer course.
It is important that your recent sexual partners are told so they can be tested and treated. Your sexual health clinic can help with partner notification — this is called contact tracing. The process is confidential. You can ask the clinic to notify partners on your behalf if you prefer.
You will be asked to attend for follow-up blood tests after treatment to check that your antibody levels are falling as expected. Your doctor or sexual health team will let you know how often these are needed.
Syphilis increases your risk of getting and passing on other sexually transmitted infections, including HIV. If you have syphilis, your doctor may offer you tests for other STIs at the same time.
If you are pregnant and have syphilis, treatment is very important. Untreated syphilis in pregnancy can cause miscarriage, stillbirth, or serious illness in the baby. Penicillin treatment during pregnancy is safe and effective.
What can affect your results
- Time since infection: antibodies may not appear in the blood until several weeks after exposure. A test taken too soon after infection may give a false negative result.
- Stage of infection: some tests are more reliable at certain stages. Your doctor or laboratory will use the right combination of tests for your situation.
- Other conditions: non-treponemal tests can give a false positive result in conditions including lupus, Lyme disease, pregnancy, and some viral infections. Specific confirmatory tests are used to check this. False positive results can also happen if a person has grown up in a tropical area and had a previous yaws, pinta or bejel infection.
- HIV infection: false negative results have been reported in people with HIV, particularly in secondary and latent syphilis. Your doctor will take this into account.
- Previous treated infection: treponemal tests usually remain positive for life after infection, even after successful treatment. Your doctor needs to know your testing history to interpret results correctly.
Other tests you might need
Because syphilis is a sexually transmitted infection, your doctor will often offer tests for other STIs at the same time. These may include:
If late syphilis is suspected, your doctor may also arrange imaging or a lumbar puncture to check for involvement of the brain or nervous system.
About syphilis
Syphilis is a bacterial sexually transmitted infection caused by Treponema pallidum. It spreads through direct contact with a syphilis sore during sexual activity. It can also be passed to babies during pregnancy. It is highly treatable but can cause serious long-term complications if untreated. For more information, visit NHS: syphilis.