A diuretic is a substance that increases the production of urine — as an adjective, causing increased urine flow. The medical diuretics — thiazides, loop diuretics like furosemide — are mainstays of hypertension and heart-failure treatment, forcing the kidneys to excrete sodium and water and so lowering blood volume and pressure. Milder natural diuretics include caffeine, alcohol, and various herbal teas such as dandelion leaf, which increase urine output through gentler mechanisms. The therapeutic logic is fluid removal; the risk is overdoing it — dehydration, potassium loss, and kidney strain. Athletes and dieters have misused diuretics for rapid weight loss, losing water rather than fat and courting dangerous electrolyte shifts. Used properly under supervision, they are among the most valuable drugs in cardiovascular medicine; used casually, they are a shortcut to imbalance.