The first thing you do in the morning:pee, even if you haven't had much to drink in the evening.
Your kidneys filter less urine at night. Your bladder also rests and therefore absorbs more urine. The hormone vasopressin makes your cells retain more water. The combination of these factors ensures that your bladder is full in the morning.
Read also: 'Do you have to urinate more often because of alcohol?'
And one more thing:if you start your day with a cup of coffee, that also makes you have to pee. The same goes for other drinks with caffeine.
