Uric Acid in Urine

Test Overview

The uric acid urine test measures the amount of uric acid in a sample of urine collected over 24 hours. Uric acid is produced from the natural breakdown of your body's cells and from the foods you eat.

Most of the uric acid is removed from the body in urine. A small amount passes out of the body in stool. But if too much uric acid is being produced, the level in the urine will increase. If the kidneys are not able to remove it from the blood normally, the level of uric acid in the urine will decrease.

High blood levels of uric acid in the body can cause solid crystals to form within joints. This causes a painful condition called gout. If gout remains untreated, uric acid crystals can build up in the joints and nearby tissues, forming hard lumpy deposits called tophi. High levels of uric acid in the urine can cause kidney stones.

Why It Is Done

A uric acid urine test is done to:

  • Check to see if kidney stones may be caused by high uric acid levels in the body.
  • Find the cause of a high level of uric acid in the blood and help choose the proper treatment.

How To Prepare

No special preparation is required before having a uric acid urine test. It is not necessary to restrict fluids or foods before the test. Be sure to drink enough fluids during the 24-hour urine test to prevent dehydration.

During the collection period, do not drink alcohol, because alcohol reduces the amount of uric acid eliminated by the kidneys.

Many medicines can change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results may mean. To help you understand the importance of this test, fill out the medical test information formmedical test information form(What is a PDF document?).

How It Is Done

A uric acid urine test is usually done on a sample taken from all the urine produced in a 24-hour period.

To collect your urine for 24 hours:

  • You start collecting your urine in the morning. When you first get up, empty your bladder 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's office or lab will usually provide you with a large container that holds about 1 gal (4 L). The container has a small amount of preservative in it. Urinate into a small, clean container and then pour the urine into the large container. Do not touch the inside of the container with your fingers.
  • Keep the large container in the refrigerator for the 24 hours.
  • Empty your bladder for the final time at or just before the end of the 24-hour period. Add this urine to the large container and record the time.
  • Do not get toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample.

How It Feels

There is no pain while collecting a 24-hour urine sample.

Risks

There is no chance for problems while collecting a 24-hour urine sample.

Results

The uric acid urine test measures the amount of uric acid in a sample of urine collected over 24 hours.

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

Results are usually available in 1 to 2 days.

Uric acid in urine1
Normal:

250–750 milligrams (mg) per 24-hour urine sample

1.48–4.43 millimoles (mmol) per 24-hour urine sample

Women typically have slightly lower uric acid levels than men.

Many conditions can change uric acid levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.

What Affects the Test

Failing to collect exactly 24 hours of urine during a uric acid urine test can cause inaccurate test results.

High values

High uric acid levels may be caused by:

Low values

Low uric acid levels may be caused by:

  • Gout, when uric acid production is normal but uric acid removal by the kidneys is reduced.
  • Kidney damage or disease that prevents the kidneys from filtering uric acid out of the blood into the urine.
  • Folic acid deficiency or lead poisoning.
  • Not eating enough protein.
  • Some medicines, such as allopurinol, insulin, some diuretics, and high levels of aspirin.
  • Drinking alcohol during the collection period.

What To Think About

  • Having a high uric acid level does not mean that you have gout. If your uric acid level is high and you do not have any other symptoms, you will not need to take any medicine to decrease your uric acid level.
  • If you have kidney disease or have had a problem with kidney stones, your doctor may start treatment with a medicine, such as allopurinol, even if your uric acid levels are not too high.
  • Uric acid also may be measured in blood. To learn more, see the topic Uric Acid in Blood.
  • About 10 out of 100 kidney stones are made of uric acid. These white or orange stones are hard to see on an abdominal X-ray. Uric acid stones can form when urine has a low pH (is very acidic). People who have gout are at high risk of developing uric acid kidney stones. Allopurinol (such as Zyloprim) may be prescribed without doing a 24-hour uric acid urine level test if a person has significantly impaired kidney function or tophi. Tophi are chalky, white accumulations of uric acid crystals that build up in the soft tissue of a joint, often occurring in the joints of fingers. Tophi may also develop in the cartilage of the external ear, the back of the fingers, or the elbow.
  • The chance of having high levels of uric acid in the urine increases under some conditions, such as from receiving chemotherapy for some types of cancer.
  • If the urine uric acid is greater than 750 mg per 24-hour urine sample, a person with gout is usually treated with a medicine such as allopurinol that decreases the body's production of uric acid. A person in this situation is called an "overproducer."
  • If the urine uric acid is less than 750 mg per 24-hour urine sample, a person with gout may be treated with a medicine such as probenecid (for example, Probalan) that increases uric acid elimination by the kidneys. A person in this situation is called an "underexcretor."
  • A person with tophi or uric acid kidney stones will be treated for high uric acid levels no matter what the results of the uric acid test are.

Related Information

References

Citations

  1. Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

Other Works Consulted

  • Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.

Credits

By Healthwise Staff
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer Nancy Ann Shadick, MD, MPH - Internal Medicine, Rheumatology
Current as of June 12, 2012

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