D-Mannose is a naturally occurring simple sugar that your body uses to help cleanse the urinary tract and maintain a healthy bladder lining. It is metabolized only in small amounts, and excess amounts are quickly excreted in the urine, so it will not interfere with health. regulation of blood sugar. Clinical studies have shown that when taken regularly, D-Mannose promotes normal urinary tract function by cleansing and maintaining the health of the bladder lining.