Uric acid is a waste product formed by the breakdown of certain types of amino acids called purines. Foods that are high in purines include liver, kidney, peas and beans (legumes), and some fish. Uric acid is also produced by the breakdown of the body's cells.

Most uric acid is eliminated from the body in urine; the rest of it passes out of the body in stools. However, if the kidneys are not able to remove uric acid from the blood normally, its level in the blood will increase and its level in the urine will drop.

High blood levels of uric acid can cause the excess to be deposited in the joints, leading to a form of arthritis called gout. If gout remains untreated for several years, uric acid crystals can build up in the joints and surrounding connective tissues, forming hard deposits called tophi. High levels of uric acid may also lead to kidney failure or result in the formation of uric acid kidney stones. 

This test is done on a sample of urine that has been collected for 24 hours (a 24-hour urine sample).

Uric Acid in Urine
Results

Normal values may vary from lab to lab.

Women generally have slightly lower uric acid levels than men.

Greater than normal values may mean

• High levels of uric acid in urine can be caused by the increased breakdown of body cells resulting from gout, some types of cancer (including leukemia and multiple myeloma), anemia (such as hemolytic anemia or sickle cell anemia), polycythemia vera, hepatitis, or Wilson's disease.
• A very high-protein diet (when the proteins are high in purines) can also cause high levels of uric acid in the urine.
• Certain kidney conditions (such as Fanconi's syndrome) may cause the kidneys to excrete too much uric acid, resulting in high levels of uric acid in the urine.

Lower than normal values may mean

• Low levels of uric acid in urine can occur in some people with gout, when uric acid production is normal but its removal by the kidneys is reduced.
• Low levels of uric acid in urine can indicate 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 can cause low levels of uric acid in the urine.
• A diet very low in protein can cause low levels of uric acid in the urine.