References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Trichomoniasis and chlamydia are two different STIs that can cause overlapping symptoms — discharge, pain on urination and genital discomfort. Because the symptoms can look alike, it’s easy to assume one when the other is actually present. Proper testing is essential to get the right treatment.
Here’s how they differ and how they’re diagnosed.
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The Two Infections
| Feature | Trichomoniasis | Chlamydia |
|---|---|---|
| Cause | Parasite (Trichomonas vaginalis) | Bacteria (Chlamydia trachomatis) |
| Most common discharge | Frothy, yellow-green, often smelly | Often no discharge; can be thin and watery |
| Itching | Very common | Less common |
| Pain on urination | Common | Common |
| Often silent? | Up to 50% | Up to 70% |
| Complications | Possible preterm birth, PID | PID, ectopic pregnancy, infertility |
| Treatment | Metronidazole | Doxycycline (7 days) |
Why They’re Confused
Both can cause:
- Vaginal or urethral discharge
- Painful urination
- Genital itching or discomfort
- Pain during sex
- No symptoms at all
A doctor can’t reliably tell them apart from symptoms alone. Testing is essential.
Testing Differences
Modern testing has made diagnosis more reliable:
- NAAT tests can detect chlamydia, gonorrhoea and trichomoniasis from the same sample
- Microscopy can identify trichomonas in real-time in clinics but is less sensitive than NAAT
- Symptom-only diagnosis is unreliable
Home test kits vary in what they cover. Check whether the kit includes trichomoniasis if you want it tested.
Treatment
Because the infections are caused by different organisms (parasite vs bacteria), treatment is different:
- Trichomoniasis — metronidazole (oral tablets)
- Chlamydia — doxycycline for 7 days
Using the wrong antibiotic won’t treat the other infection. This is why testing matters.
Partner Notification
Both infections need partner notification. Sexual health clinics can help with this confidentially. Partners should be tested and treated to prevent reinfection.
Read more: What is chlamydia? | What is trichomoniasis? | Untreated trichomoniasis
Frequently Asked Questions
Can I have both at the same time?
Yes. Co-infections are possible. Comprehensive STI testing catches this.
Does a regular STI test check for trichomoniasis?
Not always. Some standard screens only cover chlamydia and gonorrhoea. Ask your service whether trichomoniasis is included, especially if you have symptoms.
Can chlamydia treatment cure trichomoniasis?
No. Doxycycline treats bacterial infections; trichomoniasis needs metronidazole, which targets parasites.
Related reading
- Can You Get Chlamydia From Kissing?
- Can You Have Chlamydia and Test Negative?
- How Common Is Chlamydia in the UK?
- Multi-Site STI Testing: Genital, Rectal and Throat
- What Is Mycoplasma Genitalium?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
