• On day 1, urinate into the toilet upon arising in the morning.
• Collect all subsequent urine (in a special container) for the next 24 hours.
• On day 2, urinate into the container in the morning upon arising.
• Cap the container. Keep it in the refrigerator or a cool place during the collection period. Label the container with your name, the date, the time of completion, and return it as instructed.

For an infant, thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on your infant. For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia. Place a diaper over the infant (bag and all).

The infant should be checked frequently and the bag changed after the infant has urinated into the bag. For active infants, this procedure may take a couple of attempts -- lively infants can displace the bag, causing an inability to obtain the specimen. The urine is drained into the container for transport to the laboratory.

Deliver it to the laboratory or your health care provider as soon as possible upon completion.

The laboratory analyzes the specimen for the amount of citric acid present.

A below-normal result indicates possible renal tubular acidosis and a tendency to form calcium stones.

Urine citric acid levels may also be decreased with:

• severe muscular activity
• acidosis
• hypoparathyroidism
• diabetes
• chronic renal failure

Urine citric acid levels may be increased with:

• a high carbohydrate diet
• estrogen therapy
• Vitamin D