Diuretic is a substance that promotes the formation of urine by the kidney. (The word "diuretic" comes from a combination of the Greek "dia-", thoroughly + "ourein", to urinate = to urinate thoroughly). Diuresis may be due to a huge number of causes including metabolic conditions such as diabetes mellitus (in which the increased glucose level in the blood causes water to be lost in the urine); substances in food and drink (such as coffee, tea, and alcoholic beverages); and specific diuretic drugs.