An overactive bladder can be caused by many factors. These include: too much caffeine, too little fluid intake, and loss of oestrogen to the bladder lining following menopause. If you regularly drink tea, coffee or cola, you could help yourself by switching to decaffeinated beverages. Many people reduce their fluid intake because they believe drinking less will make them go less. In fact the opposite is true because low fluid intake results in concentrated urine, which can irritate the bladder lining. It is important to drink as much fluid as you feel like during the day, though you may want to limit your fluids about 3 hours before going to bed.