Zetia is a prescription drug licensed for the treatment of several conditions, including high cholesterol and a rare genetic condition called sitosterolemia. The drug works in the digestive tract by blocking the absorption of cholesterol from foods that you eat. Zetia is effective at decreasing total cholesterol and "bad cholesterol," as well as slightly decreasing triglycerides. By itself, Zetia has little effect on "good cholesterol." Zetia comes as a tablet taken once a day with or without food. While Zetia is used as a way to lower cholesterol, anyone with high cholesterol should also make certain lifestyle modifications, such as eating a low-cholesterol diet, getting regular physical exercise, and losing weight if necessary. Among the common side effects of Zetia are fatigue, diarrhea, and headache.