Kidney Stone Testing: What Blood and Urine Tests Show

What Is Kidney Stone Testing?

Kidney stone testing looks for the reasons a person forms stones. Stones are hard deposits that build up in the kidneys when substances in urine become concentrated enough to crystallize. Testing focuses on finding the metabolic cause so that future stones can be prevented.

Testing usually combines blood tests with a 24-hour urine collection. Imaging such as a CT scan or ultrasound may also be used to find a stone, but lab testing explains why it formed.

Blood Tests for Kidney Stones

Blood tests check kidney function and the substances that can drive stone formation:

• Creatinine and blood urea nitrogen, to measure kidney function
• Uric acid, because high levels can lead to uric acid stones
• Calcium, to look for high blood calcium, which can raise urine calcium
• Electrolytes such as sodium and potassium
• Sometimes parathyroid hormone, when calcium is high

These tests are simple blood draws and are often grouped into a metabolic panel.

The 24-Hour Urine Test Explained

A 24-hour urine test is the centerpiece of kidney stone evaluation. Instead of a single sample, you collect all urine over a full day into a provided container. The lab then measures the total amount of stone-forming and stone-preventing substances you excrete.

The collection usually starts in the morning after you discard the first urine of the day, and it ends with the first urine of the next morning. Keeping the container cool and following the instructions exactly matters, because an incomplete collection can give misleading results.

What the Results Can Show

Results are interpreted together, not in isolation, because several factors interact.

Who Should Be Tested

Testing is most useful for people who:

• Have had more than one kidney stone
• Formed a stone at a young age
• Have a family history of stones
• Have a stone linked to a known metabolic condition
• Have gout or high uric acid

A first-time, uncomplicated stone may not need full testing, but recurrent stones usually do.

How to Order Kidney Stone Testing

Direct-access lab testing lets you order blood tests, a 24-hour urine collection, or both without a doctor visit. You order online, pick up a collection container if needed, complete the collection, and drop it at a local CLIA-certified lab. Blood draws can be done at the same lab. Results return through a secure online account, usually within two to four business days for the urine test.

How Much Does Kidney Stone Testing Cost?

A uric acid blood test commonly costs about $25 to $50, and a creatinine test about $20 to $45. A full 24-hour urine stone panel, which measures several substances at once, typically runs about $80 to $200. Bundled blood and urine testing often falls between about $100 and $250. Direct-access pricing is paid out of pocket and does not require insurance.

Substances such as calcium and uric acid rise and fall throughout the day and change with meals and hydration. A single urine sample captures only one moment and cannot show how much you excrete over time. A 24-hour collection adds up the total output across a full day, which gives a far more accurate picture of stone risk. That is why it is the standard test for evaluating recurrent stones.

Imaging tests such as CT or ultrasound find a stone and show its size and location. Lab testing answers a different question: why the stone formed. Both kinds of information matter. After a stone is treated, metabolic testing is what guides changes that can lower the chance of another one. Knowing the cause turns a one-time event into something you can act on.

This guide is educational information, not medical advice. A clinician should interpret your results and advise on prevention.

For blood tests, no special preparation is usually needed. For the 24-hour urine collection, follow the container instructions closely. Keep the container refrigerated or cool as directed, avoid letting the collection run short, and note any medications you take. A complete, well-handled collection is what makes the results trustworthy, so the effort you put into the collection directly affects how useful the test is.