In essence, you should have a bladder full of urine but not overfull. Generally most people, need to take 2 glasses of water (around 500 ml, 2 hours prior). After you drink any fluid, it takes 2 hours to reach the urinary bladder. There is no point in coming to the Uroflow Lab and then drinking water. You will then have to wait for 2 hours. You cannot speed up the process of urine filling in the bladder.
If you have not passed stools on the day of your test, it is better to reschedule the test for another day when you have cleared your bowels well. If you are unable to do so without a laxative, inform the doctor
and take a laxative/enema.
As mentioned earlier, there is no need to take more fluids if you already had fluids. Patience is the key to doing a normal test.