Overactive bladder is a problem with bladder storage function causing a sudden urge to urinate. This urge may be difficult to suppress, and can lead to the involuntary leakage of urine also known as urge urinary incontinence. Symptoms of overactive bladder may include urinary frequency, which is urinating eight or more times within a 24 hour period. You may also experience nocturia awakening two or more times at night to urinate.