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Uric acid - blood

Definition

Uric acid is a chemical created when the body breaks down substances called purines. Purines are found in some foods and drinks, such as liver, anchovies, mackerel, dried beans and peas, beer, and wine.

Most uric acid dissolves in blood and travels to the kidneys, where it passes out in urine. If your body produces too much uric acid or doesn't remove enough if it, you can get sick. High levels of uric acid in the body is called hyperuricemia.

This test checks to see how much uric acid you have in your blood.

See also: Uric acid - urine

How the test is performed

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

A laboratory specialist checks the blood sample for uric acid.

How to prepare for the test

You should not eat or drink anything for 4 hours before the test unless told otherwise. Your doctor may also tell you to stop taking any drugs that may affect the test results. NEVER stop taking any medicine without talking to your doctor.

Drugs that can increase the level of uric acid in your body include:

• Alcohol
• Ascorbic acid
• Aspirin
• Caffeine
• Cisplatin
• Diazoxide
• Diuretics
• Epinephrine
• Ethambutol
• Levodopa
• Methyldopa
• Nicotinic acid
• Phenothiazines
• Theophylline

Drugs that can decrease the level of uric acid in your body include:

• Allopurinol
• Azathioprine
• Clofibrate
• Corticosteroids
• Estrogen
• Glucose
• Guaifenesin
• Mannitol
• Probenecid
• Warfarin

How the test will feel

Why the test is performed

This test is done to see if you have high levels of uric acid in your blood. High levels of uric acid can cause gout or kidney disease.

Your doctor may also order this test if you have had or are about to have certain types of chemotherapy. Rapid weight loss, which may occur with such treatments, can increase the amount of uric acid in your blood.

Normal Values

Normal values fall between 3.0 and 7.0 mg/dL.

Note: Normal values may vary slightly from laboratory to laboratory.

What abnormal results mean

Greater-than-normal levels of uric acid (hyperuricemia) may be due to:

• Acidosis
• Alcoholism
• Diabetes
• Gout
• Hypoparathyroidism
• Lead poisoning
• Leukemia
• Nephrolithiasis
• Polycythemia vera
• Renal failure
• Toxemia of pregnancy
• Purine-rich diet
• Excessive exercise
• Chemotherapy-related side effects

Lower-than-normal levels of uric acid may be due to:

• Fanconi syndrome
• Wilson's disease
• Syndrome of inappropriate antidiuretic hormone (SIADH) secretion
• Low purine diet

Additional conditions under which the test may be performed:

• Chronic gouty arthritis
• Injury of the kidney and ureter

What the risks are

Special considerations

References

Terkeltaub R. Crystal deposition diseases. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 294.