If you find that you’re constantly having to wake during the night to go to the toilet and often there’s barely any urine to get rid of, then you may be suffering from overactive bladder at night. This happens because even though there’s less urine, the urine that is present is much more acidic and concentrated. If your bladder is particularly sensitive, it may react by spasming and this will lead to you feeling the need to empty your bladder more frequently.