Trichomoniasis Diagnosis & Treatment

Medically reviewed by Peter Chen, MD, FACOGWritten by the Healthline Editorial Team on March 15, 2012

How Is Trichomoniasis Diagnosed?

Other conditions-such as bacterial vaginosis, yeast infections, allergic or chemical reactions, or other STDs-can cause symptoms similar to those seen in trichomoniasis. To test for T. vaginalis, then, your doctor takes a sample of your vaginal discharge and examines it under a microscope. This exam, called a wet mount, can be used to identify the unique pear shape and twitching motion of trichomoniasis.

Sometimes, T. vaginalis may be found during a Papanicolaou (Pap) smear, a diagnostic test used to screen for cervical cancer. However, Pap smears are less accurate in identifying T. vaginalis. If a Pap smear does show signs of T. vaginalis, your doctor confirms this by examining the vaginal discharge under a microscope.

Another helpful finding is an increase in the pH (acidity or alkalinity) of the vagina. Normally, the vaginal pH is 3.8 to 4.2. When trichomoniasis is present, the pH is usually greater than 5.0.

What Are the Current Treatments for Trichomoniasis?

Oral metronidazole (Flagyl) has been the treatment of choice for trichomoniasis since its introduction in the 1960s. Three treatment regimens are considered acceptable:

  • 2 grams (gm) of metronidazole, just once;
  • 500 milligram (mg) twice daily, for seven days; or
  • 250 mg three times daily, for seven days.

Many physicians prefer the single dose because it is less expensive and more convenient for the patient.

Metronidazole is also available as an intravaginal gel, but this form is only recommended for treating bacterial vaginosis. Because trichomoniasis involves not only the vagina, but also nearby glands and the urethra, local treatments (intravaginal gel) often cannot achieve a complete cure.


Metronidazole and alcohol can be a harmful combination. Metronidazole prevents the complete breakdown of alcohol by the liver and causes abdominal cramps, nausea, vomiting, headache, and flushing when taken with alcohol. If you are prescribed metronidazole, it is essential that you delay the start of medication until at least one day after your last alcoholic beverage. You should continue to abstain until one day after completing treatment.

Your sexual partner(s) also should be treated with metronidazole. When both partners are treated, cure rates are close to 90%. The most common reasons for treatment failures are poor compliance and failure to treat the partner.

Drug Resistance

Resistance to metronidazole is a less common cause of treatment failure. When an infectious organism is resistant (tolerant) to a drug, the drug is not sufficient to kill it. The problem of metronidazole-resistant T. vaginalis is slowly but steadily increasing.

When trichomoniasis is resistant to standard doses of metronidazole, other approaches become necessary. Physicians have found some success by increasing the dose, extending the number of treatment days, or using a combination of oral, intravaginal, and intravenous metronidazole. Examples of the extended regimens include metronidazole by mouth 400 mg, three times daily for seven to 10 days or 2 gm daily for 2-3 days.

If you are treated with a high dose of metronidazole, watch for signs of toxicity. These may include nausea, vomiting, metallic taste, itching, dizziness, seizures, abnormal sensations in the hands or feet, and pain, redness, or swelling of the tongue or gums. If you have any of these side effects, tell your doctor immediately.

If you are given a higher dose of metronidazole, but your symptoms still do not improve, your doctor may suggest a metronidazole susceptibility test, which can confirm the presence of metronidazole-resistant T. vaginalis and provide a guide to the amount of metronidazole needed to kill the organism. In addition, tinidazole, a medicine similar to metronidazole, has also been effective for many patients who do not respond to metronidazole. It is typically taken in a 2-gram dose by mouth, daily for seven to 14 days.

A few patients have been prescribed non-conventional treatments, with some reported success. These approaches include use of intravaginal nonoxynol-9, paromomycin cream, zinc sulfate, betadine, and acetic acid douches. However, clinical trials have not evaluated the effectiveness of these agents, so they are not typically recommended.

Lastly, if vaginal symptoms persist despite treatment, your doctor will reconfirm that the symptoms are indeed due to trichomoniasis. This is important since other medical conditions produce similar symptoms.

Important Notice for Pregnant Women in Their First Trimester!

If you have trichomoniasis but no symptoms and are in your first trimester of pregnancy, treatment is not recommended. This is based on the long-held belief that metronidazole (the standard drug for this infection) used at this time may cause birth defects. However, numerous studies since 1965 have all failed to show that first trimester use of metronidazole is associated with any increase in congenital abnormalities. In all likelihood, metronidazole does not increase the rate of birth defects but until further studies are conducted, doctors generally try to avoid this drug during the first trimester.

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