Overactive bladder (OAB) is a common condition that affects millions of Americans. Overactive bladder isn’t a disease; it is the name of a group of urinary symptoms involving problems with bladder-storage function. The most common symptom of OAB is a sudden urge to urinate that you can’t control. Some people will leak urine when they feel the urge. Leaking urine is called “incontinence.” Having to go to the bathroom many times during the day and night is another symptom of OAB.