Uric acid is a chemical created when the body breaks down substances called purines. Purines are found in some foods and drinks, such as liver, anchovies, mackerel, dried beans and peas, beer, and wine.

Most uric acid dissolves in blood and travels to the kidneys, where it passes out in urine. If your body produces too much uric acid or doesn't remove enough of it, you can get sick. High levels of uric acid in the body is called hyperuricemia.

This test checks to see how much uric acid you have in your urine.

See also: Uric acid - blood

A 24-hour urine sample is needed.

• On day 1, urinate into the toilet when you get up in the morning.
• Afterwards, collect all urine in a special container for the next 24 hours.
• On day 2, urinate into the container when you get up in the morning.
• 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 the infant. For males, place the entire penis in the bag and attach the adhesive to the skin. For females, place the bag over the labia. Diaper as usual over the secured bag.

This procedure may take a couple of attempts -- lively infants can move the bag, causing the urine to be absorbed by the diaper. Check the infant frequently and change the bag after the infant has urinated into it. Drain the urine from the bag into the container provided by your health care provider.

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

Your doctor may tell you to stop taking any drugs that may affect the test results. For example, high levels of vitamin C and dyes used during certain x-rays may cause incorrect results.

Drugs that can interfere with test results include:

• Alcohol
• Allopurinol
• Anti-inflammatory drugs (such as ibuprofen)
• Salicylates (including aspirin)
• Thiazide diuretics
• Probenecid

This list may not be all-inclusive.

The test involves only normal urination, and there is no discomfort.

This test may be done to diagnose kidney stones. It may also be used to monitor people with gout, since many of these patients develop uric acid kidney stones.

Normal values range from 250 to 750 milligrams per 24 hours.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Higher than normal uric acid levels in the urine may be due to:

• Cancers that have spread (metastasized)
• Disorders that affect the bone marrow or certain white blood cells
• High-purine diet
• Gout
• Rhabdomyolysis
• Lesch-Nyhan syndrome
• Fanconi syndrome

Lower than normal uric acid levels in the urine may be due to:

• Long-term alcohol use
• Chronic glomerulonephritis
• Lead poisoning

Goldman L, Ausiello D. Cecil Textbook of Medicine. 22nd ed. Philadelphia, Pa: WB Saunders; 2004.

McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. St. Louis, Mo: WB Saunders; 2006.