When the human body is retained for urine routine, mainly morning urine is retained for delivery, and when the urine routine is retained, mainly the middle urine is retained. If the patient retains two specimens at close intervals in the morning, they can be mixed, but preferably no more than half an hour. If the two urine samples are taken at longer intervals, bacteria may be mixed in. Also the composition of the urine varies from time to time, so mixing is not recommended. For this reason, it is a good idea to collect urine in the morning, and to collect a sufficient amount of urine for testing at one time. If there is difficulty in urinating each time, try to collect and mix the urine specimens at close intervals, usually not more than half an hour. Some patients have less urine and it is recommended that they drink plenty of water prior to urine collection to ensure sufficient urine is available for specimen delivery.