A uric acid test measures how much uric acid is in your blood or urine. Uric acid is a waste product your body creates when it breaks down purines, chemicals found naturally in your cells and in many foods and drinks. Most uric acid dissolves in your blood, travels through your kidneys, and leaves your body in urine. The test checks whether too much is building up or too little is being produced, both of which can signal health problems.
Why Your Doctor Orders This Test
The most common reason for a uric acid blood test is to help diagnose or monitor gout, a painful form of arthritis caused by uric acid crystals collecting in a joint. A blood draw is usually paired with a synovial fluid analysis, where a small sample of fluid is taken directly from the affected joint, to confirm the diagnosis.
The second major reason is cancer treatment monitoring. When chemotherapy or radiation kills cancer cells rapidly, those dying cells release large amounts of purines into the bloodstream all at once. Your body converts those purines into uric acid, and the sudden spike can overwhelm your kidneys. This is called tumor lysis syndrome, and it can cause kidney failure, dangerous heart rhythms, and seizures. Uric acid levels are tracked closely during treatment, typically from three days before to seven days after therapy begins, so a spike can be caught and treated early. A uric acid level that rises more than 25% from baseline or exceeds 8 mg/dL is one of the markers used to identify this syndrome.
A urine version of the test serves a different purpose. It helps determine whether high uric acid is behind recurring kidney stones, and it monitors kidney stone risk in people who already have gout.
Blood Test vs. Urine Test
The blood test is straightforward. A healthcare professional draws a small sample from a vein in your arm, and results are typically available within a day or two. This version measures the concentration of uric acid circulating in your bloodstream at that moment.
The urine test requires a 24-hour collection. You’ll receive a special container and instructions to collect every drop of urine over a full day. The sample can be stored at room temperature or refrigerated. You’re usually asked to eat your normal diet in the 24 hours leading up to the collection so the results reflect your typical uric acid output. This version tells your doctor how efficiently your kidneys are clearing uric acid from your body, which is information a single blood draw can’t provide.
Normal Uric Acid Levels
Reference ranges differ by age and sex because hormones, body composition, and kidney function all influence uric acid metabolism. The standard ranges for a blood test are:
- Adult males: 4.0 to 8.5 mg/dL
- Adult females: 2.7 to 7.3 mg/dL
- Children: 2.5 to 5.5 mg/dL
- Newborns: 2.0 to 6.2 mg/dL
Women tend to have lower levels than men until menopause, when levels gradually rise and begin to approach male ranges. Keep in mind that labs may use slightly different cutoffs, so always compare your number to the reference range printed on your specific report.
What High Levels Mean
A result above your reference range is called hyperuricemia. It doesn’t automatically mean you have gout or kidney stones, but it raises the likelihood of both. When uric acid exceeds what your blood can dissolve, it forms sharp, needle-like crystals. Those crystals can settle in joints (causing gout flares) or accumulate in the kidneys (forming uric acid stones).
High uric acid has two basic causes: your body is producing too much, or your kidneys aren’t clearing enough. Common contributors include:
- Diet: Foods high in purines raise production. Shellfish like lobster and shrimp, organ meats, and red meat are well-known sources. Drinks sweetened with high fructose corn syrup, including many sodas, also drive levels up.
- Kidney function: If your kidneys aren’t filtering efficiently, uric acid backs up in the blood. Chronic kidney disease is one of the most common reasons for persistently elevated levels.
- Cell turnover: Conditions that cause rapid cell destruction, including certain cancers and their treatments, flood the blood with purines.
- Alcohol: Beer and liquor both increase uric acid production and reduce the kidneys’ ability to excrete it.
Research has also linked chronically high uric acid to heart disease, high blood pressure, diabetes, fatty liver disease, and metabolic syndrome. The relationship doesn’t always mean uric acid caused those conditions, but the association is strong enough that an elevated level may prompt your doctor to screen for other metabolic risk factors.
What Low Levels Mean
Low uric acid is less common and gets less attention, but it can also point to underlying issues. Levels below the normal range may indicate liver disease (including Wilson’s disease, a genetic condition that causes copper to accumulate in the body), Fanconi syndrome (a kidney disorder that causes excessive loss of nutrients through urine), or unusually low purine intake. Certain medications can also push levels down. If your result comes back low, your doctor will typically look at the broader picture of your liver and kidney function to understand why.
Uric Acid and Kidney Function
Because the kidneys are responsible for clearing uric acid, the test is sometimes interpreted alongside creatinine, another waste product that reflects how well your kidneys are filtering. When kidney function declines, both uric acid and creatinine tend to rise, but for different reasons. Researchers have found that looking at the ratio of uric acid to creatinine can help separate people whose uric acid is high because their body overproduces it from those whose levels are high because their kidneys aren’t keeping up. This distinction matters because the two situations call for different management approaches.
How to Prepare
Most labs do not require fasting for a uric acid blood test, though your doctor may ask you to fast if other blood work is being drawn at the same time. For the 24-hour urine collection, eating your standard diet beforehand gives the most accurate picture of your baseline excretion. Let your provider know about any medications or supplements you’re taking, since some can affect results. Alcohol and high-purine foods in the days before testing can temporarily inflate your numbers, so your doctor may advise you to avoid them if the goal is to get a clean baseline reading.
Reading Your Results
A single uric acid number is a snapshot, not a diagnosis. Levels fluctuate throughout the day and can swing significantly based on what you ate or drank recently. A high result on one test usually leads to a repeat test or additional workup rather than an immediate diagnosis. If you have gout, your doctor will likely order this test periodically to track whether your levels are staying in a target range, typically below 6 mg/dL, which is the threshold where existing crystals begin to dissolve over time.
For people being monitored during cancer treatment, the test may be repeated daily or even more frequently during the highest-risk window. The goal is to catch a dangerous rise before it damages the kidneys, and the treatment team will adjust hydration and medications based on each result.