Trichomoniasis is diagnosed by testing a sample of vaginal fluid or urine, and the most accurate option is a nucleic acid amplification test (NAAT), which finds the parasite's DNA. The older wet-mount microscope exam misses many infections. Most people get a quick swab, urine cup, or exam, with results back in a few days.
most common curable STI
metronidazole / tinidazole
retest
| Item | Value |
|---|---|
| Estimated US infections | ~2.6 million — most common curable STI |
| Have no symptoms | ~70% |
| Cure | >90% — metronidazole / tinidazole |
| Reinfected within 3 mo | ~1 in 5 — retest |
How trichomoniasis is tested
Trichomoniasis is caused by Trichomonas vaginalis, a single-celled protozoan parasite — not a bacterium or virus — and it's the most common curable STI CDC. Because the organism lives in the urogenital tract, the sample comes from there: a vaginal swab (which you can often collect yourself), female urine, or a sample taken during a pelvic exam.
The test that matters most is the NAAT, which amplifies and detects the parasite's genetic material. NAATs (such as the Aptima T. vaginalis assay) are the preferred method because they're highly sensitive — roughly 95 to 100% CDC, 2021 — meaning they rarely miss a true infection. For women, vaginal swabs and urine both perform well.
You may still encounter two older methods. Wet-mount microscopy puts a drop of vaginal fluid under a microscope so a clinician can spot the moving parasites in real time — it's fast and cheap, but it only works if enough live, motile organisms are present and someone looks quickly, so it misses a large share of real infections. Rapid antigen tests detect parasite proteins at the point of care and are faster than a lab NAAT but less sensitive. If a wet mount is negative and trichomoniasis is still suspected, a NAAT is the right next step.
When to test after exposure
When symptoms appear, they typically show up 5 to 28 days after infection — though they can surface much later, and many people never get symptoms at all. Because the parasite needs time to multiply to detectable levels, testing too soon after a single exposure can come back falsely negative. If you have symptoms, get tested when they start; if you're testing after a known exposure without symptoms, give it time and read up on when to test after exposure so you don't test in the blind window.
If your first test is negative but symptoms persist, retesting is reasonable — a NAAT after the window has passed is the most reliable way to confirm.
Who should get screened
Trichomoniasis lands disproportionately on women, who account for over 80% of an estimated 2.6 million infections in the US US prevalence, 2018. Screening guidance focuses on those at highest risk and those for whom an infection carries extra consequences:
- Women living with HIV should be screened routinely each year, even without symptoms, because untreated trichomoniasis can worsen HIV transmission risk.
- Anyone with symptoms — vaginal discharge, itching, irritation, or burning with urination — should be tested rather than treated on a guess.
- People with a new or multiple partners, or whose partner was diagnosed, benefit from testing because the infection is often silent.
- Anyone already getting checked for other STIs can usually add a trichomoniasis NAAT to the same visit.
If you're not sure whether what you're feeling fits, our guide to trichomoniasis symptoms in women walks through what's typical and what isn't.
Getting tested: what the visit or at-home kit is like
Testing is simpler than most people expect. In a clinic, you'll either provide a urine sample in a cup or have a swab taken — often one you collect yourself in a private room. At-home kits ship a self-collected vaginal swab to a lab. Either way, there's no fasting, no blood draw needed for this one, and results usually come back in a few days.
Cost rarely has to be a barrier. Testing is free or low-cost at health departments, Planned Parenthood, and Title X clinics, and many insurers cover STI screening. You can get tested through a clinic or a mail-in service, and it helps to compare testing providers on price, turnaround, and which tests are included before you commit.
A common mistake is assuming a basic STI panel covers trichomoniasis — it doesn't always. Confirm that the test ordered specifically includes T. vaginalis, ideally by NAAT, since some panels still rely on the less sensitive wet mount.
Reading your results
A NAAT result is straightforward: positive means the parasite's DNA was detected and you have trichomoniasis; negative means it wasn't found. Because NAAT sensitivity is so high, a negative result is reassuring as long as you tested after the window. A negative wet mount is less conclusive — it can mean you're clear, or it can mean the test simply didn't catch the parasites that were there.
| Test | Sample | Sensitivity | Speed |
|---|---|---|---|
| NAAT (preferred) | Vaginal swab or female urine | ~95–100% | Results in a few days |
| Wet-mount microscopy | Vaginal fluid | Lower — misses many cases | Same visit |
| Rapid antigen | Vaginal fluid | Lower than NAAT | Point-of-care, minutes |
If your result is positive
Trichomoniasis is curable. Treatment is a defined course of antibiotics — see our full guide to trichomoniasis treatment for the regimens, including why guidelines now prefer a multi-day metronidazole course over the old single dose for women.
Two practical points: finish every pill even after you feel better, and ask whether your partner needs treating too. If only one of you is treated, you can pass it back and forth — this ping-pong reinfection is one of the most common reasons trichomoniasis comes back.
When to see a clinician
See a clinician if you have new vaginal discharge, itching, irritation, or pain with urination or sex; if a partner has been diagnosed; or if you've tested positive and your symptoms haven't cleared after finishing treatment. Pregnant people with symptoms should be evaluated, and anyone with HIV should keep up the recommended yearly screening. A diagnosis here is common and treatable — clinics handle it every day, and it says nothing about you as a person.