Same thing happens to me whenever the dose goes up, including one really long pee.
I'm taking 8 mg reta plus half a milligram of elora each week and the scale keeps moving down. I wake up at least twice, sometimes three or four times, to pee during the night, plus a big one first thing in the morning. That can mean a two-pound difference between bedtime and morning weigh-in. At almost sixty my bladder doesn't hold what it used to, so the trips are shorter, but the urge is still strong. Blood sugar stays between 5.4 and 5.8 and both glucose and blood pressure are better than before I started. I don't drink much right before bed. I'm wondering if the medication is making the liver convert fat into liquid that then has to come out as urine.