Tinidazole is used to treat trichomoniasis (a sexually transmitted disease that can affect men and women), giardiasis (an infection of the intestine that can cause diarrhea, gas, and stomach cramps), and amebiasis (an infection of the intestine that can cause diarrhea, gas, and stomach cramps and can spread to other organs such as the liver). Tinidazole is also used to treat bacterial vaginosis (an infection caused by an overgrowth of harmful bacteria in the vagina) in women. Tinidazole is in a class of medications called nitroimidazole antimicrobials.