Frequency has several causes. First, the kidneys lose their ability to concentrate urine and conserve water, which leads to an increase in urine production. Secondly, the bladder has an increased frequency of involuntary bladder contractions in approximately 10-20 percent of the population over 65, which leads to the sense of urgency, as well as frequency. The amount of urine left in the bladder after urinating increases to 75-100 milliliters, which is slightly less than one-half cup of liquid. The sensation to urinate occurs when there is less urine in the bladder. Often the need to urinate occurs at 150-300 milliliters, which is approximately one-half to one-and one-third cup of liquid. The amount of urine the bladder can hold decreases to 300-600 milliliters, which is approximately one and one-third cup to two and one-half cups, due to decrease muscle tone of the bladder. Imagine, if there is 75 milliliters left in the bladder at the end of voiding, and the sensation to void occurs at as little as 150 milliliters, and the bladder will only hold 150 milliliters; it is understandable why people are experiencing frequency