Uric Acid
At a Glance
Why Get Tested?
To detect high levels of uric acid in the blood, which could be a sign of the condition gout or to monitor uric acid levels when undergoing chemotherapy or radiation treatment; to detect high levels of uric acid in the urine in order to diagnose the cause of kidney stones and to monitor those with gout who are at risk of developing such stones
When to Get Tested?
When you have joint pain or other symptoms that your doctor suspects may be due to gout; when you have had or are going to have certain chemotherapy or radiation therapies for cancer; when you have recurrent kidney stones; when you have gout or are otherwise at risk for kidney stone formation
Sample Required?
A blood sample drawn from a vein in the arm or a 24-hour urine sample
Test Preparation Needed?
None may be needed; however, some institutions recommend fasting. Follow any instructions you are given.
The Test Sample
What is being tested?
Uric acid is produced by the breakdown of purines, which are nitrogen-containing compounds found in the body in substances such as DNA. Purines enter the blood primarily from the normal breakdown and turnover of cells in the body and to a lesser extent from the digestion of certain foods (such as liver, anchovies, mackerel, dried beans and peas) and drinks (alcoholic beverages like beer and wine). Most uric acid is removed from the body by the kidneys and is excreted in the urine; the remainder is eliminated in the stool.
If too much uric acid is produced or not enough is excreted, it can accumulate in the body and cause increased levels in the blood (hyperuricemia). The presence of excess uric acid can cause gout, a condition characterized by inflammation that occurs in joints when crystals derived from uric acid form in the joint (synovial) fluid. Excess uric acid can also lead to kidney disease.
The accumulation of too much uric acid is due to either increased production, decreased elimination, or some combination of both. Increase production can be caused by, for example, increased cell death as may be seen with some cancer therapy or rarely an inherited tendency to overproduce uric acid. Decreased elimination of uric acid is often a result of impaired kidney function due to kidney disease. In many cases, the exact cause of excess uric acid is unknown.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in your arm. A 24-hour urine sample may be collected for the urine uric acid test.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation may be needed. Some institutions, however, recommend fasting for 8-12 hours. Follow any instructions that you are given and be sure to discuss any medications that you are taking with your physician before having this test performed.
The Test
How is it used?
The uric acid blood test is used to detect high levels of this compound in the blood in order to help diagnose gout. The test is also used to monitor uric acid levels in people undergoing chemotherapy or radiation treatment. Rapid cell turnover from such treatment can result in an increase in uric acid.
The uric acid urine test is used to help diagnose the cause of recurrent kidney stones and to monitor people with gout for stone formation.
When is it ordered?
The uric acid blood test is ordered when a doctor suspects high levels of uric acid. Some patients with high levels of uric acid have a disease called gout, which is a form of arthritis. People with gout suffer from joint pain, most often in their toes, but in other joints as well. The test also is ordered as a monitoring test when someone with cancer has undergone chemotherapy or radiation, to learn whether uric acid levels are getting dangerously high.
The uric acid urine test may be ordered when a person suffers from recurrent kidney stones or has gout and needs to be monitored for formation of these stones.
What does the test result mean?
Blood
Higher than normal uric acid levels in the blood is called hyperuricemia and can be caused by the over-production of uric acid in the body or the inability of the kidneys to clear out enough uric acid. The doctor will need to investigate further to determine the cause of the overproduction or decreased excretion of uric acid. There are several genetic inborn errors that effect purine metabolism. Metastatic cancer, multiple myeloma, leukemias, and cancer chemotherapy can cause increased production of uric acid. Chronic renal disease, acidosis, toxemia of pregnancy, and alcoholism can cause decreased excretion.
Increased concentrations of uric acid can cause crystals to form in the joints, which can lead to the joint inflammation and pain characteristic of gout. Uric acid can also form crystals or kidney stones that can damage the kidneys.
Low levels of uric acid in the blood are seen much less commonly than high levels and are seldom considered cause for concern. Although low values can be associated with some kinds of liver or kidney diseases, Fanconi syndrome, exposure to toxic compounds, and rarely as the result of an inherited metabolic defect (Wilson disease), these conditions are typically identified by other tests and symptoms and not by an isolated low uric acid result.
Urine
High uric acid levels in the urine are seen with gout, multiple myeloma, metastatic cancer, leukemia and a diet high in purines. Those at risk of kidney stones who have high uric acid levels in their urine may be given medication to prevent stone formation.
Low urine uric acid levels may be seen with kidney disease and chronic alcohol use.
Is there anything else I should know?
Many drugs can increase or decrease the level of uric acid. In particular, diuretic drugs like thiazide drugs can cause uric acid levels to go up.
Aspirin and other salicylates have varying effects on uric acid. At low aspirin levels (as may occur in persons taking aspirin only occasionally), aspirin can increase blood uric acid. On the other hand, in high doses (as may be used to treat rheumatoid arthritis), aspirin actually lowers the concentration of uric acid.
For people who have uric acid kidney stones or gout, foods that are high in purine content should be avoided, including organ meats (like liver and kidneys), sardines and anchovies. Alcohol also should be avoided, because it slows down the removal of uric acid from the body. Fasting, a starvation diet, stress, and strenuous exercise all raise uric acid levels.
Although the uric acid test cannot definitively diagnose gout, a test for monosodium urate in synovial fluid (joint fluid) can.
Common Questions
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Article Sources
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
NIAMS. Fast Facts about Gout. (Revised March 2007). Available online at http://www.niams.nih.gov/Health_Info/Gout/gout_ff.asp through http://www.niams.nih.gov. Accessed June 2010.
MedlinePlus Medical Encylopedia. Uric acid - blood. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003476.htm. Accessed June 2010.
MedlinePlus Medical Encylopedia. Uric acid- - urine. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003616.htm. Accessed June 2010.
Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. 3rd Edition, St. Louis: Mosby Elsevier; 2006, Pg 530.
Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. 4th edition, St. Louis: Mosby Elsevier; 2010 Pp. 536, 998.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 1098-1101.
MayoClinic.com. High uric acid level. (Last updated September 13, 2008). Available online at http://www.mayoclinic.com/health/high-uric-acid-level/MY00160 through http://www.mayoclinic.com. Accessed June 25, 2010.
The Gout and Uric Acid Education Society. Uric Acid. Available online at http://gouteducation.org/patient/about-gout/uric-acid/ through http://gouteducation.org. Accessed June 25, 2010.
Mosby's Diagnostic and Laboratory Test Reference, 3rd Edition. Pagana and Pagana. 1997. Pp. 842-845.
(August 2002) Dincer H, Dincer A, Levinson D. Asymptomatic hyperuricemia: To treat or not to treat. Cleveland Clinic Journal of Medicine, vol. 69, no. 8, Pp 594-608. Available online at http://www.ccjm.org/content/69/8/594.full.pdf+html through http://www.ccjm.org. Accessed October 2010.
Sources Used in Previous Reviews
Laboratory Tests & Diagnostic Procedures with Nursing Diagnoses (4th edition), Corbett, JV. Stamford, Conn.: Appleton & Lang, 1996. Pp. 105-109.
A Manual of Laboratory & Diagnostic Tests (sixth edition), Frances Fischbach, editor. Philadelphia: Lippincott Williams& Wilkins, 2000; Pp. 396-397.
Nader Rifai, PhD. Department of Laboratory Medicine, Children's Hospital, Boston, MA.
