Uric Acid in Blood

The blood uric acid test measures the amount of uric acid in a blood sample. 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 filtered out by the kidneys and passes out of the body in urine. A small amount passes out of the body in stool. But if too much uric acid is being produced or if the kidneys are not able to remove it from the blood normally, the level of uric acid in the blood increases.

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

A uric acid blood test is done to:

• Help diagnose gout.
• Check to see if kidney stones may be caused by high uric acid levels in the body.
• Check to see if medicine that decreases uric acid levels is working.
• Check uric acid levels in people who are undergoing chemotherapy or radiation therapy. These treatments destroy cancer cells that then may leak uric acid into the blood.

You do not need to do anything before you have this test.

Some 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 indicate. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

The health professional who takes a sample of your blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Put a gauze pad or cotton ball over the needle site as the needle is removed.
• Put pressure on the site and then put on a bandage.

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

There is very little chance of a problem from having a blood sample taken from a vein.

• You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
• In rare case, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
• Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

The blood uric acid test measures the amount of uric acid in a blood sample.

Normal

Normal values of blood uric acid may vary from lab to lab. Results are usually ready within 1 to 2 days.

Uric acid crystals sometimes form in joints even at levels less than 7 mg/dL, especially in men. This can lead to a gout attack, even though the uric acid levels are within the normal range.

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 medical history.

High values

High uric acid values may be caused by:

• Individual differences in the way your body produces or gets rid of uric acid.
• Conditions, such as:
  • Kidney disease or kidney damage.
  • The increased breakdown of body cells that occurs with some types of cancer (including leukemia, lymphoma, and multiple myeloma) or cancer treatments, hemolytic anemia, sickle cell anemia, or heart failure.
  • Other disorders, such as alcohol dependence, preeclampsia, liver disease (cirrhosis), obesity, psoriasis, hypothyroidism, and low blood levels of parathyroid hormone.
  • Starvation, malnutrition, or lead poisoning.
  • A rare inherited gene disorder called Lesch-Nyhan syndrome.
• Medicines, such as some diuretics, vitamin C (ascorbic acid), lower doses of aspirin (75 to 100 mg daily), niacin, warfarin (such as Coumadin), cyclosporine, levodopa, tacrolimus, and some medicines used to treat leukemia, lymphoma, or tuberculosis.
• Eating foods that are very high in purines, such as organ meats (liver, brains), red meats (beef, lamb), game meat (deer, elk), some seafood (sardines, herring, scallops), and beer.

Low values

Low uric acid values may be caused by:

• Severe liver disease, Wilson's disease, or some types of cancer.
• The syndrome of inappropriate antidiuretic hormone (SIADH), a condition that causes large amounts of fluid to build up in the body.
• Not eating enough protein.
• Sulfinpyrazone, large amounts of aspirin (1,500 mg or more daily), probenecid (such as Benemid and Probalan), and allopurinol (such as Aloprim and Zyloprim).

• Some medicines may increase the level of uric acid in the blood. These include diuretics, theophylline (such as Theo-Dur, Theo-X, and Theochron), low-dose aspirin (75 to 100 mg daily), and some medicines used to treat tuberculosis.
• The vitamin niacin, high doses of vitamin C, caffeine, and a substance found in chocolate and tea (theobromine) can cause uric acid levels to be inaccurately high.
• Excessive use of alcohol, starvation, a high-protein diet, or strenuous exercise can raise the level of uric acid in the blood.

• 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.
• A high level of uric acid in the blood does not always mean that a person with a painful joint has gout. Testing the fluid taken from an affected joint for the presence of uric acid crystals is the only sure method to diagnose gout. For more information, see the medical test Joint Fluid Analysis.
• Uric acid may also be measured in urine. If your blood uric acid level is high, a 24-hour urine collection may help determine whether your body is producing too much uric acid or your kidneys are not getting rid of enough of it. For more information, see the medical test Uric Acid in Urine.
• Uric acid blood levels vary from day to day. The level is usually higher in the morning and lower in the evening.
• Blood uric acid levels that increase during pregnancy, even if the levels remain within the normal range, may help diagnose preeclampsia.

Other Works Consulted

• Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.

• Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

• Handbook of Diagnostic Tests (2003). 3rd ed. Philadelphia: Lippincott Williams and Wilkins.

• Pagana KD, Pagana TJ (2002). Mosby’s Manual of Diagnostic and Laboratory Tests, 2nd ed. St. Louis: Mosby.