Your doctor may ask you to collect your urine for 24 hours so that he or she can determine the type of kidney stone you have. The test can also measure urine volume, pH, and other substances that may contribute to urinary problems.

• The collection period usually starts in the morning. When you first get up, urinate but do not save this urine. Write down the time that you urinated to mark the beginning of your 24-hour collection period.
• For the next 24 hours, collect all your urine. Your doctor will usually provide you with a large container that holds about 1 gal (3.8 L) and has a small amount of preservative in it. Urinate into a smaller, clean container and then pour the urine into the large container. Avoid touching the inside of the container with your fingers.
• Keep the large container in the refrigerator during the collection period.
• Urinate for the final time at or just before the end of the 24-hour period. Add this urine to the large container and write down the time.
• Avoid getting toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample.