Uric Acid

What is uric acid?

Uric acid is a waste product formed when substances called purines, released during cell renewal and taken in with food, are broken down in the body. Purines are especially abundant in organ meats, red meat, some seafood and alcoholic drinks such as beer; drinks sweetened with fructose can also increase uric acid production. Most of the uric acid formed is excreted in the urine via the kidneys, and some through the intestines.

When uric acid production increases or its excretion by the kidneys decreases, its level in the blood rises. If high levels persist for a long time, uric acid crystals can build up in the joints and cause gout, or build up in the kidneys and lead to stone formation. Uric acid is also a substance with an antioxidant effect in the blood, so it is normal for it to be present at a certain level. The test is performed on the serum portion of blood drawn from the arm, using a method involving the enzyme uricase.

When is a uric acid test ordered?

The uric acid test is most often ordered when gout is being investigated in people with joint pain and swelling, and to monitor treatment in patients diagnosed with gout. It is also evaluated in people with a history of kidney stones when the type and cause of the stone are being investigated. During some cancer treatments that increase cell breakdown, regular measurements may be taken to detect a sudden rise in uric acid. It may also be ordered as part of a general metabolic assessment in conditions such as kidney disease or metabolic syndrome.

• Sudden pain, swelling and redness, especially in the big toe
• A history of kidney stones or recurrent stone formation
• Monitoring of uric acid-lowering treatment in gout
• Treatments that increase cell breakdown, such as chemotherapy
• Kidney disease, metabolic syndrome or diuretic use

How do you prepare for a uric acid test?

Because uric acid levels can be affected by diet, it is usually recommended that you fast for about 8 hours before the test and give your blood in the morning. It is best to stay away from alcohol and from heavy meals based on organ meats and red meat the day before, as these can temporarily raise uric acid. Very intense exercise and dehydration can also temporarily increase the value.

Low-dose aspirin, diuretics and some other medications can raise uric acid, while some medications can lower it. Simply tell your doctor about your medications and supplements; do not stop any medication on your own, including your uric acid-lowering treatment. If you wish, a nurse can take your blood at your home or workplace in the morning before breakfast.

What does a uric acid result mean?

High uric acid, or hyperuricemia, results either from overproduction of uric acid or from inadequate excretion by the kidneys. The main causes include a purine-rich diet, alcohol, fructose-containing drinks, excess weight, kidney disease, diuretics, dehydration, psoriasis, and blood cancers and their treatment. High uric acid does not always mean gout; in many people it causes no symptoms at all.

On the other hand, the blood uric acid level may be normal during a gout attack; this is why the diagnosis is not based on this test alone. Low uric acid is rare and may be associated with certain medications, severe liver disease or excessive excretion by the kidneys. Because values are generally higher in men, reference ranges are given separately by sex and may also vary by age and laboratory; the laboratory's own range is shown on this page. Your uric acid result should be interpreted by your doctor together with your joint symptoms and other tests.