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Uric acid - urine

Definition

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. Purines are also a part of normal body substances, such as DNA.

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 may 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

How the test is performed

A 24-hour urine sample is needed. See: 24-hour urine collection.

How to prepare for the test

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.

How the test will feel

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

Why the test is performed

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

Normal Values

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.

What abnormal results mean

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

What the risks are

References

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

Bazari H. Approach to the patient with renal disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 115.