The collection period usually starts in the morning. When you first get up (say 6 am), empty your bladder, but do not collect this urine. Note down that time to mark the beginning of your 24 hour collection period. For the next 24 hours, collect all the urine whenever you pass. However you should empty your bladder for the final collection at or just before the end of the 24 hour collection period (6 am). Add the final sample to the large container and record the time.