STI Retesting After Treatment: Test of Cure vs Reinfection Screening

If you've been treated for a sexually transmitted infection (STI), retesting is often the step that closes the loop. It confirms the infection has gone, so you can have sex again without passing it on, and it catches a new infection if you've been exposed again. There are two different reasons to retest, with different timing: a test of cure and reinfection screening. Getting the timing right is what makes the result meaningful, and it's easy to arrange with an at-home STI test.

What Is STI Retesting After Treatment?

STI retesting after treatment means having another STI test after you've finished your antibiotics or other treatment. It answers one of two questions:

• Did the treatment work? This is a test of cure. It checks that the original infection has been cleared.
• Have I caught it again? This is reinfection screening. It checks for a new infection, for example from a partner who wasn't treated, or a new partner, after sex without a condom.

Not every STI needs both, and some don't need either. Your doctor will tell you which applies to you; the sections below explain the usual advice.

Test of Cure vs Reinfection Screening: The Differences

Which STIs Need Retesting After Treatment?

1. Gonorrhoea

Gonorrhoea is caused by the bacterium Neisseria gonorrhoeae, which has become resistant to several antibiotics that used to cure it. That's why a test of cure matters more for gonorrhoea than for most STIs. In the UK, the NHS retests everyone after treatment. US (CDC) guidelines advise a test of cure for throat infections, which are harder to cure, 7 to 14 days after treatment, and for anyone whose symptoms don't settle. The test is usually a PCR (NAAT), sometimes with a culture so the lab can check which antibiotics work. Everyone should then retest about 3 months later for reinfection. See the gonorrhoea test for how the test works.

2. Chlamydia

Chlamydia, caused by Chlamydia trachomatis, is cured by a course of antibiotics in almost everyone, so a test of cure isn't routine after standard treatment. It is advised if you're pregnant (about 4 weeks after treatment), if symptoms continue, if you missed doses or had sex during treatment, or if you were given a different antibiotic. Don't test sooner than 3 weeks after treatment: PCR (NAAT) tests are sensitive enough to detect DNA from dead bacteria, which can give a positive result even after a cure. Retest about 3 months after treatment, because reinfection is common. The chlamydia test page has more on sample types and timing, and chlamydia vs gonorrhoea compares the two.

3. Syphilis

Syphilis, caused by Treponema pallidum, is followed up with blood tests rather than a single test of cure. A non-treponemal test such as RPR or VDRL measures the level (titre) of antibodies, usually 6 and 12 months after treatment for early syphilis, and more often for people living with HIV. A fall in the titre, usually at least fourfold, shows the treatment has worked. The other type of syphilis test (treponemal, such as TPHA) stays positive for life, so it can't show a cure or a new infection; RPR is the test to watch. See the syphilis test for details.

4. Trichomoniasis

Trichomoniasis is a common, curable infection caused by a parasite. CDC guidelines advise women to retest within 3 months of treatment, because reinfection is common.

STIs That Don't Need a Test of Cure

Some STIs can't be cleared from the body with current treatment, so there's no cure to confirm. Instead, treatment controls the infection and lowers the chance of passing it on:

• Herpes: the virus stays in the body. Antiviral tablets shorten outbreaks and, taken daily, reduce transmission. There's no test to show it's gone.
• HPV: there's no treatment for the virus itself, and most infections clear by themselves within a couple of years. Women continue cervical screening; warts are treated if they appear.
• HIV: treatment doesn't cure HIV, but it can make the viral load undetectable, and then HIV can't be passed on through sex. Regular viral load tests replace a test of cure.
• Hepatitis B: most adults clear a new infection by themselves. Those who don't (chronic hepatitis B) have regular blood tests to monitor the liver and the virus.

Hepatitis C is different: it is curable. Antiviral tablets cure more than 95% of people, and an HCV RNA test about 12 weeks after treatment ends confirms the cure. The antibody test stays positive for life, so future checks use RNA testing. See the hepatitis C test.

Even with these infections, keep up regular screening for other STIs, which can be cured and are often silent: see STIs without symptoms.

Why Is STI Retesting After Treatment Important?

1. It confirms you're cured

Feeling better isn't proof. Chlamydia, gonorrhoea and syphilis are often silent even before treatment, so the absence of symptoms afterwards doesn't show the infection has gone. Where a test of cure or follow-up blood test is advised, it's the only way to know.

2. It catches treatment failure and antibiotic resistance

If an infection is still there after the right treatment, it may be resistant to that antibiotic. This is a growing problem with gonorrhoea. A test of cure finds it early, so you can be treated with something that works, and resistant strains can be reported and tracked. It's also why you should never treat an STI with leftover or borrowed antibiotics.

3. It finds reinfection, and protects your partners

Having had an STI doesn't make you immune, and many people catch the same infection again within months, often from a partner who wasn't treated. Retesting at 3 months finds it before it causes complications such as pelvic inflammatory disease, and before you pass it on. Until you've finished treatment (for chlamydia and gonorrhoea, until 7 days after you and your partners have been treated), avoid sex, including oral sex. If your partner was the one diagnosed, read what to do if your partner tested positive.

Where to Get STI Retesting After Treatment in Bangkok

Thai and international patients can have a test of cure or reinfection screening at public and private hospitals and sexual health clinics across Bangkok. Take your earlier result and the name of the treatment you had, if you can: it helps the doctor choose the right test and timing.

If you'd rather not sit in a clinic waiting room, Ovio's at-home STI testing brings the test to your home, condo, hotel or office anywhere in Bangkok. Tell us which infection you were treated for and when you finished treatment, and we'll suggest the right tests on the right date. A doctor takes the samples, results are reliable, and everything stays strictly confidential.

Frequently Asked Questions

How long after chlamydia treatment should I retest?

For reinfection, about 3 months after treatment. If you need a test of cure (for example, if you're pregnant or still have symptoms), wait at least 3 weeks, usually about 4 weeks, so the test doesn't pick up dead bacteria.

Do I need a test of cure for gonorrhoea?

Often, yes. It's advised for throat gonorrhoea 7 to 14 days after treatment, and UK guidance retests everyone. Either way, retest about 3 months later for reinfection.

Can I test positive after treatment even if I'm cured?

Yes, if you test too soon. PCR tests can detect genetic material from dead chlamydia or gonorrhoea bacteria for a few weeks. For syphilis, the treponemal antibody test stays positive for life, which is why RPR is used for follow-up.

My partner and I were both treated. Do we still need to retest?

Yes, for chlamydia and gonorrhoea. Guidelines advise retesting about 3 months after treatment whether or not your partner was treated, because reinfection is common.

When can I have sex again after STI treatment?

For chlamydia and gonorrhoea, wait 7 days after you and your partners have finished treatment, and until any symptoms have gone. For syphilis, wait until treatment is complete and any sores have healed. Your doctor will advise for other infections.

Is a retest the same as a normal STI test?

Usually yes: the same urine, swab or blood sample as the original test. What changes is the timing and, for syphilis, how the result is read.