i don't know anything about you to blindly determine a specific cause not even your sex. if you are male and over the age of 50 it could be bph (benign prostatic hypertrophy). if you are a female one would need to consider a urinary tract infection or variety of urinary tract problems. and in either sex nocturia (the medical name for this condition) could be one of the signs of diabetes. on a more simple case you could be drinking too much in the evening and not completely emptying your bladder. see your medical provider. this is really the only way to determine a reason and hopefully find a solution.
i have frequent urination at night. what causes that?