What is a 24-Hour Urine Uric Acid test?
This test measures the total amount of uric acid in all the urine you produce over a 24-hour period.
Uric acid is a waste product produced when your body breaks down substances called purines. Purines are found naturally in your body and are also present in certain foods and drinks.
Most uric acid is removed from your body through the kidneys and passed into your urine. Measuring the amount of uric acid excreted over 24 hours can provide information about how your body produces and eliminates uric acid.
A 24-hour urine uric acid test can provide important information to help evaluate gout, kidney stones, abnormal uric acid levels, and disorders affecting uric acid metabolism or kidney excretion.
Other names: 24-hour urine uric acid, urinary uric acid, urine urate, uric acid urine test
What is it used for?
A 24-hour urine uric acid test may be used to help:
Evaluate the cause of kidney stones
Uric acid can contribute to the formation of uric acid kidney stones. Measuring urinary uric acid can help determine whether excessive uric acid excretion may be contributing to stone formation.
Evaluate gout
Gout occurs when urate crystals accumulate in and around joints, causing inflammation and pain. A urine uric acid test can provide additional information about how your body is handling uric acid.
Determine how the body handles uric acid
The test can help distinguish between conditions in which the body produces too much uric acid and conditions in which the kidneys do not remove enough uric acid.
Monitor treatment
In some patients with gout or recurrent kidney stones, urine uric acid measurements may be used to evaluate the response to dietary changes or medications that affect uric acid metabolism.
Why do I need a 24-Hour Urine Uric Acid test?
You may need this test if:
You have recurrent kidney stones.
Your healthcare provider suspects uric acid kidney stones.
You have gout and your provider wants to evaluate your uric acid excretion.
You have an unusually high or low blood uric acid level and the cause needs to be investigated.
Your provider suspects that your kidneys are not eliminating uric acid normally.
You have a condition or treatment that may cause increased uric acid production or excretion.
Your healthcare provider wants to assess your risk of developing uric acid kidney stones.
What happens during a 24-Hour Urine Uric Acid test?
This test requires you to collect all of your urine for 24 hours in a special container provided by your healthcare provider or laboratory.
The collection generally includes the following steps:
At the beginning of the collection period, urinate in the toilet as usual. Do not collect this first urine. Record the time.
For the next 24 hours, collect all urine in the provided container.
Store the container as instructed, usually refrigerated or in a cool place during the collection period.
Exactly 24 hours after starting the test, urinate one final time and include this urine in the container.
Return the completed collection to your healthcare provider or laboratory as instructed.
It is important to collect all urine produced during the 24-hour period. Missing a urine sample can make the result inaccurate.
Will I need to do anything to prepare for the test?
Your healthcare provider may give you specific instructions about your diet, fluid intake, and medications before or during the collection.
Depending on the reason for testing, you may be asked to maintain your usual diet or follow a specific dietary plan.
Foods particularly high in purines, such as organ meats, certain seafood, and some types of meat, can affect uric acid production.
Do not stop taking prescribed medicines unless your healthcare provider tells you to do so.
Are there any risks to the test?
There are no known medical risks from collecting a 24-hour urine sample.
The main concern is accidentally missing part of the urine collection, which can affect the accuracy of the result.
What do the results mean?
The result represents the total amount of uric acid excreted in the urine during 24 hours and is commonly reported as mg/24 hours or mmol/24 hours.
The meaning of your result depends on your blood uric acid level, kidney function, diet, fluid intake, medications, and clinical condition.
A high level of 24-Hour Urine Uric Acid
A high urine uric acid level means that your body is excreting more uric acid than expected.
Possible causes include:
Increased breakdown of cells or purines
A diet high in purine-rich foods
Certain metabolic or blood disorders
Some medications
Conditions associated with increased uric acid production
Certain genetic disorders affecting purine metabolism
High urinary uric acid can increase the risk of uric acid kidney stone formation, particularly when urine is acidic or concentrated.
A low level of 24-Hour Urine Uric Acid
A low urine uric acid level may occur when the kidneys are excreting less uric acid or when the body is producing less uric acid.
Possible causes include:
Reduced kidney function
Low-purine dietary intake
Certain medications
Some liver or metabolic disorders
Conditions that cause increased reabsorption of uric acid by the kidneys
A low urinary uric acid level can sometimes be seen in people with gout when the underlying problem is reduced kidney excretion of uric acid.
Important note
A 24-hour urine uric acid result should not be interpreted by itself. It is usually evaluated together with serum uric acid, kidney function, urine volume, urine pH, dietary intake, medications, and the patient's clinical history.
For patients with kidney stones, urine volume and urine pH are particularly important because the risk of uric acid stone formation depends not only on the amount of uric acid excreted, but also on how concentrated and acidic the urine is.
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